MXPA97004623A - Barrier layer for use of derefrigera cabinets - Google Patents

Abstract

The present invention relates to a composition which is resistant to the action of polyurethane foam swelling agents, the composition comprising: i) an effective amount of a polyethylene graft copolymer, and ii) an effective amount of a copolymer rubber. of block and in addition iii) a polyolefin and / or iv) a homopolymer or styrene copolymer

Description

"BARRIER LAYER FOR USE IN REFRIGERATOR CABINETS" The invention provides compositions that are resistant to the action of polyurethane foam swelling agents, barrier layers consisting of compositions, thermoformable compounds incorporating barrier layers, methods for making thermoformable compounds, and insulating cabinet wall structures. which incorporate the thermoformable compounds, the structures being useful in apparatus constructions, particularly refrigerators and dishwashing machines. Typical refrigerator cabinets consist of an external metal cabinet, an internal plastic liner typically made of ABS (acrylonitrile-butadiene-styrene) or HIPS (high-impact polystyrene), and a core of insulation foam, usually Polyurethane foam. The swelling agents for the polyurethane foam are entangled in the foam. It is currently used commercially as the swelling agent, Freon or fluorotrichloromethane, a fully halogenated methane. However, increased amounts of environmental regulations are pressing, and in some cases demanding substitutes for Freon. The most promising substitutes for Freon are halogenated hydrocarbons containing at least one hydrogen atom. Polyurethane swelling agents, such as Freon and Freon substitutes such as 2-fluoro-2, 2-dichloroethane and 2,2-dichloro-1,1,1-trifluoroethane, can cause bladders in the lining, catastrophic cracks, cracks small (cracking), and loss of shock or impact (brittle) properties, as well as bleached by stress and / or dissolution ,, These Freon substitutes appear to be more chemically aggressive than Freon to attack the lining. It is commonly believed that the attack of the liner swelling agent occurs during cooling and condensation of the swelling agent to the liquid. Favorable conditions for these cycles occur during shipment and storage. The shipping conditions can be simulated during manufacturing by cycling the cabinet of the appliance from hot to cold, in order to cause evaporation and condensation of the puffing agent (s). Attempts by the prior art to approach this problem have involved the use of barrier layers. A main function of these layers is to prevent the attack of the swelling agents in the inner plastic lining. However, in addition to providing superior solvent resistance with respect to polyurethane foam swelling agents, barrier layer compositions must also exhibit certain processability characteristics. In particular, the compositions intended to be used as barrier layers in the construction of apparatus cabinets must be extrudable, thermoformable and re-rectifiable. The extrusion capability, as used herein, is intended to indicate that the composition can be extruded, either simultaneously or subsequently, with the materials comprising the inner plastic liner or liners to form a thermoplastic compound. Therefore, the composition of the barrier layer must be capable of adhering to the styrene-based polymers commonly used to make the inner plastic liner. Illustrative examples of styrene-based polymers are ABS, HIPS and mixtures thereof. The ability to co-extrude the barrier layer with one or more layers of the inner liner provides significant cost and efficiency advantages. In addition, the compositions of the barrier layer must be thermoformable. In particular, the composition of the barrier layer should not be detracted from the thermoformability of the composite structures incorporating these barrier layers. If the resulting compounds can not be thermoformed in the required internal cabinet configuration, the manufacturers of the appliance cabinet lose significant cost and production advantages. Those skilled in the art will appreciate that thermoformability is therefore a requirement for compositions intended to be used as barrier layers in the construction of the apparatus cabinet. Finally, the composition of the barrier layer should not negatively affect the re-correctability or recyclability of the thermoformable compound. During the manufacture of the apparatus cabinets, the thermoformed internal cabinets are typically trimmed from the excess of the composite material. The resultant trimming material is often incorporated into the virgin inner liner material, ie, the styrene-based polymer (s). As a result, the compatibility of the composition of the barrier layer with that of the materials of the inner lining is particularly important. The properties of the inner liner materials should not be adversely affected. Those skilled in the art will appreciate that the ability to recycle the excessive thermoformable composite material provides significant cost savings.

Therefore, it would be highly desirable to provide a barrier layer composition capable of exhibiting (a) superior solvent resistance to polyurethane foam swelling agents, (b) extrudability and adhesion ability with respect to internal linings and the manufacture of the composite structures, (c) thermoformability once the barrier layer has been incorporated into a composite structure, and (d) re-rectifiability with respect to the incorporation of the remaining material and the virgin lining material. Even though several attempts have been made by the prior art to solve this problem, none has provided the desired balance of properties. For example, U.S. Patent No. 5,118,174 issued to Benford et al. Discloses a multi-component laminate structure for use in insulated cabinet structures. The laminated structure of multiple components contains a barrier layer which, however, provides insufficient solvent resistant and re-proofing capability. U.S. Patent No. 5,227,245 issued to Brands et al. Discloses a barrier layer to prevent solvent attack on insulating cabinet wall structures consisting essentially of an amorphous thermoplastic polyester resin that is a copolymer copolymer adduct. an aromatic dicarboxylic acid and a material containing active hydrogen. However, polyester has extremely poor capacity with styrenic resins and therefore the barrier layer lacks the desired re-proofing capacity. Finally, U.S. Patent Nos. 5,221,136 and 5,340,208 to Hauck et al. Disclose a barrier layer comprising a polyolefin and a block copolymer rubber, which can be functionalized with maleic anhydride. However, some thermoformable compunds prepared using these barrier layers have been found to exhibit less than optimal thermoformability. It has been found in particular that the barrier layer can be bonded to the female molds used in the thermoforming process. Furthermore, these barrier layer compositions have been found to have limited re-rectification capability with internal lining materials based on styrenic materials. Therefore, an object of this invention is to provide a barrier layer composition which is resistant to the action of polyurethane foam swelling agents, and which exhibits desirable processing characteristics such as extrudability, thermoformability and re-correctability. Another object of the invention is to provide a barrier layer which is bondable to one or more of the inner liner layers to form a thermoformable composite. More particularly, an object of the invention is to provide a barrier layer that is extrudable with one or more of the inner liner layers to form a thermoformable composite. Another object of the invention is to provide a thermoformable composition containing a barrier layer which protects one or more of the inner lining layers from the action of the polyurethane foam swelling agents, and which also has desirable re-rectification compatibility with the materials which comprise the inner lining layers. Finally, an object of the invention is to provide an insulated cabinet wall structure comprising a thermoformable composite comprising a barrier layer which protects the inner lining layers from the action of the polyurethane foam swelling agents. These and other objects of the invention are provided with a specific barrier layer composition (A). The barrier layer composition (A) is resistant to the action of polyurethane foam swelling agents and comprises (i) an effective amount of a modified polyolefin, more preferably modified with a compound selected from the group consisting of maleic anhydride, maleic acid, maleic anhydride derivatives, maleic acid derivatives and mixtures thereof; and (ii) an effective amount of a rubber. Optionally, and preferably, the barrier layer composition (A) will further contain an effective amount of a polyolefin (iii), which is selected from the group consisting of polyethylene, polypropylene, polybutylene, and copolymers thereof and optionally polymers based on styrenic materials (iv). The invention further provides a thermoformable compound having a functional layer (I) comprising one or more sub-layers of one or more polymers based on styrenic materials and a barrier layer (II) adhered to at least one surface of the functional layer (I), wherein the barrier layer (II) comprises a barrier layer composition (A). The invention also provides an insulating wall cabinet structure having the thermoformable compound in combination with an external structural wall (III) and insulation (IV) of polyurethane foam adhered to both the barrier layer (II) and the wall ( III) external structure to be placed between them. Finally, the invention provides a method for manufacturing the thermoformable compound, which requires providing a functional layer (I) and adhering to the functional layer (I), a barrier layer (II). Figure 1 is a schematic drawing of a refrigerator cabinet. Figure 2 is a schematic drawing of an internal cabinet that serves as the internal plastic wall of the refrigerator of Figure 1. Figure 3 is a fragmentary cross section of the thermoformable compound that forms the internal cabinet of Figure 2. Turning now to the drawings, you can see that the Figure 1 illustrates a particularly desirable end-use application for the present invention. The refrigerator apparatus 1 has an insulating wall cabinet structure E consisting of an outer metal hull 2, the internal cabinet 3, and an insulation body 4 foamed at the site therebetween. The internal cabinet 3 is formed of thermoformable compound 5 (see Figure 2).

Turning now to Figure 3, the thermoformable compound 5 consists of a functional layer 6 and a barrier layer 7. The functional layer 6 serves as the visually pleasing portion of the interior of the refrigerator apparatus 1. In general, the functional layer 6 will consist of one or more sublayers (8, 9) of one or more polymers based on styrenic materials. Suitable examples of polymers based on styrenic materials include ABS, HIPS and mixtures thereof. A particularly preferred example is illustrated in Figure 3, wherein the functional layer 6 consists of the sublayers 8 and 9. In general, the sublayer 8 will generally provide a visually pleasing high gloss appearance, while the sublayer 9 It will generally provide desirable performance characteristics such as good resistance to food contamination and normal wear or tear. Illustrative materials particularly suitable for use as a sublayer 8, include HIPS. A particularly desirable material can be used as a sub-layer 8 is a polystyrene of medium high-impact impact strength (e.g., PS®-7800, commercially available from BASF Corporation of Yandotte, Michigan).

Suitable illustrative materials can be used as a sublayer 9 include bulk HIPS (e.g., a particularly desirable material is a high impact polystyrene, characterized by a nominal melt flow rate of 2.6 grams / 101, (measured according to condition G of the American Society for the Testing of Materials) and a Vicat softening temperature of 102 ° C, PS-7100, also commercially available from BASF Corporation) or ABS. In general, sublayers 8 and 9 will comprise functional layer 6. However, it will be appreciated that with many currently available polymer compositions, the functional layer 6 may also consist of either a single layer or more than two layers. In a particularly preferred embodiment, which is described above, the sublayer 8 will generally comprise between about 1 to 10 weight percent of the total weight of the functional layer 6, while the sublayer 9 will generally comprise between 99 percent to 90 percent by weight of the total weight of functional layer 6. More specifically, sublayer 8 comprises from 1 percent to 5 percent by weight, while sublayer 9 comprises from 99 percent to 95 percent of the total weight of functional layer 6.

The barrier layer 7 may consist of: (i) an effective amount of a modified polyolefin; and (ii) an effective amount of a rubber (iii) of polyethylene, polypropylene, polybutylene and copolymers thereof, and / or (iv) a polymer based on styrenic material. The barrier layer composition (A) will contain a modified polyolefin (i). As used herein, the term "modified polyolefin" is intended to describe polyolefin graft copolymers derived from the graft polymerization of an unsaturated carboxylic acid or its functional derivative or other vinyl functional group containing monomer to any of the polymers of olefin which will be discussed below with respect to component (iii). However, the olefin to be modified in this way preferably will be polyethylene (HDPE, LDPE, LLDPE). The unsaturated carboxylic acid or its functional derivative or other monomer containing a vinyl functional group to be grafted onto the aforementioned olefin polymers includes, for example, carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acids, itaconic and sorbic; acid anhydrides such as maleic anhydride and itaconic anhydride acid amides such as acrylamide and methacrylamide; epoxy groups contain compounds such as glycidyl acrylate, the glycidyl methacrylate hydroxyethyl group containing esters such as 2-hydroxyethyl methacrylate and polyethylene glycol monoacrylate; and metal salts for example sodium acrylate, sodium methacrylate and zinc acrylate. These graft monomers can be used alone or in combination. Among the anhydride acids which are particularly preferred are maleic anhydride and maleic acid and derivatives thereof. The proportion of the graft monomers is preferably within the molar range of 0.005 percent to 5 percent, based on component (i). A preferred embodiment of this type of polymer includes the product obtained by grafting the maleic acid or anhydride into an HDPE. The graft copolymerization of the unsaturated carboxylic acid or its functional derivative or other monomer containing the vinyl functional group in the olefin polymer can be carried out using different methods. The example, the olefin polymer, the graft monomer and the free radical initiator are mixed together and kneaded in a molten state. In another method, the graft monomer is incorporated into a solution or suspension of the olefin polymer in an appropriate solvent. An especially preferred materail for use as a modified polyolefin (i) is a modified polyolefin, characterized by a melt index of 1.2 grams per 10 minutes, which is measured according to Method D1238 of the American Society for the Testing of Materials, and a density of 0.961 gram per cubic centimeter, which is measured according to Method D1505 of the American Society for the Testing of Materials (e.g., Plexar® PX209, which can be obtained commercially from Quantum of Cincinnati, Ohio). The composition (A) of barrier layer will further comprise a rubber (ii). Suitable rubbers will usually be synthetic block copolymer rubbers. Illustrative examples include diblock of the styrene block, styrene-ethylene / butylene-styrene triblock, styrene-ethylene-butylene-styrene triblock functionalized with maleic anhydride, maleic acid or mixtures thereof, or combinations of any of the aforementioned . Particularly suitable rubbers (ii) are linear styrene-butadiene-styrene rubbers (e.g., Stereon® 840A, a linear styrene-butadiene-styrene rubber with a styrene content of 43 weight percent, a weight molecular weight of 94000, and a M / Mn value of 1.40 that can be obtained commercially from Firestone Tire &Rubber Co., and Finaclear® 520, a linear styrene-butadiene-styrene rubber with a styrene content of 43 percent in weight, a molecular weight of 85,000 and a Mw / Mn value of 1.10, commercially available from Fina of Houston, Texas. Optionally, and especially preferably, the barrier layer composition (A) will also contain a polyolefin (iii). Although the composition containing the components (i) and (ii) is capable of providing desirable performance properties, the incorporation of the polyolefin (iii) provides significant cost advantages and no significant decrease in the performance or processing properties of the barrier compositions or layers of the invention. Generally speaking, the component (iii) of polyolefin is defined to include the various types of polyethylene and propylenes, polybutylenes, and the well-known copolymers thereof. Although polyolefins other than polyethylene can provide mixtures according to the present invention, it is the group of polyethylenes that constitutes the preferred group. HDPE materials manufactured by polymerizing ethylene are included in the polyethylenes using the coordination catalysts called Ziegler-Natta to provide linear high density polyethylene (unbranched) LLPE materials (densities = 0.940 to 0.970 gram per cubic centimeter), manufactured by polymerizing ethylene using Free radical catalysts under high pressures and high temperatures to provide branched polyethylenes (densities = 0.910 to 0.934 gram per milliliter); the LLDPE materials prepared from ethylene and minor amounts of alkenes of 3 to 12 carbon atoms alpha, beta-ethylenically unsaturated under Ziegler-Natta to provide polyethylenes essentially low density linear but with alkyl side chains component alpha-olefin ( densities = 0.88 to 0.935 gram per milliliter). The high density polyethylenes are preferred within this polyethylene group as described above. In addition, polyolefins (iii) appropriate also have indices melt flow (MFI) of from 1 to 10, with the polyolefins especially preferred having MFI from 1 to 3. A particularly preferred polyolefin is the high density polyethylene characterized by density of 0.96 gram per milliliter, which is measured according to D1505 method of the American Society for Testing Materials, a melt index of 1.15 grams per 10 minutes, measured according to Method D1238 of the American Society for the Materials Test (e.g., commercially available as LM-6187 HDPE from Quantum, Cincinnati, Ohio). Finally, the barrier layer composition (A) can optionally also contain a polymer (iv) based on styrenic material. The styrenic polymer component (iv) of the present invention is a polystyrene resin or an ABS homopolymer (acrylonitrile-butadiene-styrene). Polystyrene resins include a styrene (polystyrene crystalline) copolystyrene modified with rubber homopolymer (high impact polystyrene (HIPS)). Polystyrene is a high molecular weight polymer preferably having a molecular weight (weight average) greater than about 150,000 grams per mole. The rubber modified polystyrene, which is especially preferred, is a well known material which is polystyrene modified by an elastomer such as polybutadiene or a copolymer of styrene and butadiene. This material is described, for example, in Modern Plastics Encycopedia, McGraw-Hill, page 72 (1983-1984). It can be prepared by polymerizing the styrene monomer in the presence of polybutadiene or a copolymer of styrene and butadiene. The ABS copolymer resins that can be used in the present invention are well known to those skilled in the art, the preparation of this material is disclosed, for example, in U.S. Patent Nos. 3,563,845; 3,565,746 and 3,509,237 all of which are incorporated herein by reference. In general, the barrier layer composition (A) can generally have from (i) 1 to 70 parts by weight of a modified polyolefin; (ii) 1 to 40 parts by weight of a rubber, (iii) 0 to 90 parts by weight of a polyolefin and (iv) 0 to 50 parts by weight of a polymer to -base of styrenic material, wherein the components ( i) to (iv) are added to the total weight of composition A of the barrier layer. A preferred barrier layer composition will have from (i) 5 to 40 parts by weight of a modified polyolefin, (ii) 5 to 30 parts by weight of a rubber, (iii) 20 to 80 parts by weight of a polyolefin and ( iv) 0 to 48 parts by weight of a polymer based on styrenic material, wherein components (i) to (iv) are added to the total weight of composition A of the barrier layer. Particularly preferably, the barrier layer composition of the invention will have from (i) 5 to 30 percent parts by weight of a modified polymer, (ii) 5 to 20 percent parts by weight of a rubber, (iii) 30 to 70 weight percent of a polyolefin; and (iv) 0 to 30 weight percent of a polymer based on styrenic material, wherein components (i) to (iv) are added to the total weight of the polymer. the barrier layer composition. Two particularly preferred embodiments of the barrier layer composition (A) will be noted below: Modality # 1 Modality # 2 [parts by weight] [parts in weight] Modified Polyolefin (i) 15-25 15-25 Rubber (i) 10-20 10-20 Polyolefin (iii) 60-70 35-45 Styrene Polymer (iv) 20-40 Components (i) - (iv ) of the composition (A) of the barrier layer will be processed by well-known processing methods in order to form a homogeneous mixture. The mixture can be granulated as necessary or can be immediately formed into a layer by well-known polymer processing techniques. Now going back to thermoformable compound 5, the barrier layer 7 will normally be from 1 percent to 50 percent by weight of the total weight of the compound 50, while the functional layer 6 will be from 50 percent to 99 percent by weight, based on the weight of the compound 5. More particularly, the layer 6 will function and the barrier layer 7 will comprise respectively from 70 percent to 99 percent by weight and from 30 percent to 1 percent by weight of the total weight of the compound 5. It is especially preferred if the compound 5 has from 80 percent to 95 percent of functional layer 6 and from 5 percent to 20 percent by weight of barrier layer 7. Particularly preferably, the thermoformable compound 5 will be formed by simultaneous co-extrusion of the barrier layer 7 directly towards the sub-layer 9. In this preferred embodiment, the sub-layer 9 will be coextensive with and will adhere to the sub-layer 8. Alternatively , a barrier layer 7 manufactured above can subsequently be laminated to the functional layer 6 and more preferably to the sub-layer 9. Those skilled in the art will appreciate that well-known lamination technologies involving the application of increased heat and / or pressure , are sufficient to form the thermoformable compound 5. The thermoformable compound 5 will generally be thermoformed into a cabinet structure of the apparatus in a manner as illustrated in Figure 2 as the internal cabinet 3. Those skilled in the art will appreciate that these processing techniques are well known in the art and generally involve a die cutting process using male and female cooperation molds. It will be appreciated that for most molding operations, a surface of the barrier 7 will be oriented outwardly away from the interior of the internal cabinet 10 and will therefore remain in contact with the female mold. Correspondingly, an aspect of desirable thermoformability is that the barrier layer 7 does not adhere to the female mold during the thermoforming process. The internal thermoformed cabinet 3 is then assembled with the outer hull so that there is a free space between them. A polyurethane foam composition is placed therein and its foam in situ between the inner cabinet 3 and the outer helmet 2 to form the foamed insulation 4 on the site. The resulting structure of the internal cabinet 3, the external hull 2 and the foamed insulation 4 at the site between them is defined herein as being an insulating wall cabinet structure E. The external helmet 2 may comprise well known materials suitable for use, such as the external surface of a construction of the apparatus. Although hard rigid plastics may be suitable, metal is especially preferred. In the present invention, the foamed insulation 4 at the preferred site is the polyurethane foam. The polyurethane foam can be prepared by intimately mixing, under reaction conditions, an organic polyisocyanate with a reactive isocyanate, a compound containing active hydrogen such as for example a polyol, in the presence of a swelling agent, and introducing the foam-forming mixture. inside the space between the internal cabinet 3 and the external metal helmet 2 of the cabinet. The swelling agents used in the preparation of the polyurethane are generally organic compounds having an atmospheric boiling temperature of about -50 ° C to about + 100 ° C. In general, these compounds selected for this purpose are halogenated organic compounds, especially those containing fluorine and / or chlorine, since this also helps to give good thermal insulation properties to the foam. In the present invention, the preferred swelling agent to be used to prepare the polyurethane foam 4 is that which comprises a hydrohalocarbon. Hydrohalocarbons are preferred in relation to perhalogenated carbon compounds due to their finally lower ozone depletion potentials, although the use of perhalogenated carbon compounds such as trichlorofluoromethane and diclofluoromethane in small amounts is not excluded from the present invention. Suitable hydrohalocarbon compounds include hydrochlorofluorocarbons, hydrofluorocarbons and hydrochlorocarbons, particularly those having 1 to 3 carbon atoms, due to their appropriate boiling temperatures. Preferred swelling agents for preparing the insulating polyurethane foam used in the present invention include dichlorofluoroethane and its isomers, chlorodifluoroethanes and their isomers, tetrafluoroethane and its isomers and 1,1,1-trichloroethane because of its availability, ease of handling and properties. desirable physical properties of the polyurethane foams prepared therewith. However, those skilled in the art will appreciate that the use of other polyurethane foam swelling agents is within the scope of the present invention. The swelling agent is employed in amounts sufficient to provide a foam having a total bulk density of from about 10 to about 200, preferably from about 15 to about 100 and more preferably from about 18 to about 60 kilograms per cubic meter. The active hydrogen-containing compounds which are useful in the preparation of the polyurethane foam, include those materials having two or more groups containing active hydrogen atoms which can react with an isocyanate. Together, these compounds are referred to as poliahls. Preferred among the polyahl compounds are those having at least two hydroxyl groups, primary or secondary amine, carboxylic acid or thiol groups per molecule. Polyols, ie, compounds having at least two hydroxyl groups per molecule are especially preferred because of their desirable reactivity with the polyisocyanates. Suitable isocyanate reactive materials for preparing rigid polyurethanes include those having a molecular weight of from about 50 to about 700, preferably from about 70 to about 300, and especially from about 70 to about 150. These reactive materials of isocyanate also advantageously have a functionality of at least 2, preferably about 3 to about 16, preferably up to about 8, of active hydrogen atoms per molecule. Additional suitable isocyanate-reactive materials include polyether polyols, polyester polyols, polyhydroxy-terminated acetal resins, hydroxyl-terminated amines and polyamines, and the like. Especially preferred for preparing rigid foams on the basis of performance, availability and cost, is a polyether polyol prepared by adding an alkylene oxide to an initiator having from about 2 to about 8, preferably from about 3 to about 8. active hydrogen atoms. Polyisocyanates useful in making polyurethanes include aromatic, aliphatic and cycloaliphatic polyisocyanates and combinations thereof. Representative of these types are diisocyanates, such as n- or p-phenylene diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, hexamethyl-1,5-diisocyanate, tetramethyl-1,4-diisocyanate. , cyclohexane-1,4-diisocyanate, hexahydrotoluene diisocyanate (and isomers), naphthalene-1,5-diisocyanate, l-methylphenyl-2,4-phenyldiisocyanate, diphenylmethane-4,4'-diisocyanate, biphenylmethane-2, 4 ' -diisocyanate, 4, 4 '-biphenylene diisocyanate, 3, 3'-dimethoxy-4,4'-biphenylene diisocyanate and 3,3'-dimethyldiphenylpropan-4,' -diisocyanate; triisocyanates such as toluene-2,4,6-triisocyanate and polyisocyanates such as 4,4'-dimethyldiphenylmethane-2,2 ', 5'-5'-tetraisocyanate and the various polymethylene polyphenyl polyisocyanates. A crude polyisocyanate may also be used in the practice of this invention, such as the crude toluene diisocyanate obtained by the phosgenation of a mixture of diamines of toluene or the crude diphenylmethane diisocyanate obtained by the phosgenation of crude diphenylmethanediamine. Especially preferred are polyphenyl polyisocyanates connected with methylene because of their ability to crosslink the polyurethane. The diisocyanate index (equivalent isocyanate equivalents ratio of the groups containing the active hydrogen) is advantageously from 0.9 to about 5.0, preferably from about 0.9 to about 3.0 and more preferably from about 1.0 to about 1.5. In addition to the typical components mentioned above, it is often desirable to employ certain other ingredients to prepare the cellular polyurethane. Among these additional ingredients are water, catalyst, surfactant, flame-retardant agent, preservative, colorant, antioxidants, reinforcing agents, filler or filler and the like. Water is often used in paper as a precursor of the puffing agent and processing aid. The water can react with the isocyanate leading to the generation of carbon dioxide gas which then functions as a swelling agent in the foam-forming reaction. When present, the water of preference is used in amounts not exceeding about 7 parts, preferably about 6 parts and more preferably about 5 parts by weight per 100 parts by total weight of the compound (s) containing active hydrogen I presented. The beneficial effects can be seen when at least about 0.5 part and preferably at least about 1 part water per 100 parts of total weight of the active hydrogen-containing compound (s) is present. It is possible to use amounts of water that exceed these scales but the resultant foam may have undesirable physical properties, such as poor dimensional stability and poor thermal insulation. In making the polyurethane foam, it is generally especially preferred to employ a small amount of a surfactant to stabilize the foam-forming reaction mixture until it is covered. These surfactants advantageously comprise a liquid or solid organosilicone surfactant. Other less preferred surfactants include polyethylene glycol ethers of long chain alcohols, tertiary amine salts or alkanolamine of long chain alkyl acid sulfate ethers, alkylsulfonic esters, alkylarylsulfonic acids. These surfactants are used in sufficient amounts to stabilize the foam-forming reaction mixture against crushing and the formation of unequal large cells. Typically, it will generally be sufficient for this object from about 0.2 part to about 5 parts of the surfactant per 100 parts by total weight of the active hydrogen-containing compound (s) present. Advantageously one or more catalysts are used for the reaction of the active hydrogen-containing compound (s) with the polyisocyanate. Any suitable urethane catalyst can be used, including tertiary amine compounds and organometallic compounds. Exemplary tertiary amine compounds include triethylene diamine, n-morpholine, pentamethyl diethylenetriamine, tetramethylenediamine, l-methyl-4-dimethylaminoethylpiperazine, 3-methoxy-N-diethylpropyl Lamin, N-ethylmorpholine, diethylene ethanolamine, N, N-dimethyl- N ', N' -dimethyl-isopropylproliendia ina, N, N-diethylene-3-diethylaminopropylamine, dimethylbenzylamine and the like. Exemplary organometallic catalysts include organomercury catalysts, organoplome, organophtols and organotin, with organotin catalysts being preferred among these. Suitable tin catalysts include stannous chloride, tin salts of carboxylic acids, such as dibutyltin di-2-ethyl hexanoate as well as other organometallic compounds. A catalyst for the trimerization of the polyisocyanates, such as alkali metal alkoxide, may also be optionally employed herein. these catalysts are used in a condition that measurably increases the reaction rate of the polyisocyanate. Typical amounts are from about 0.001 part to about 1 part of the catalyst per 100 parts by total weight of the active hydrogen-containing compound (s) present.

In making the polyurethane foam, the compound (s) containing active hydrogen, polyisocyanate and other components are contacted, mixed thoroughly and allowed to react, and expanded and cured in a cellular polymer. The specific mixing apparatus is not critical and various types of mixing head and spraying apparatuses can conveniently be used. It is often convenient but not necessary to pre-mix certain of these raw materials before the polyisocyanate components and those containing active hydrogen react. For example, it is often useful to mix the active hydrogen-containing compound (s), the swelling agent, the surfactants, the catalysts and other components except for the polyisocyanates, and then to contact this mixture with the polyisocyanate . Alternatively, all the components can be introduced individually into the mixing zone, where the polyisocyanate and the polyol (s) are contacted. It is also possible to pre-react all or a portion of the active hydrogen-containing compound (s) with the polyisocyanate to form a prepolymer, even when this is not preferred.

EXAMPLES The following examples are provided to illustrate the invention and are not to be construed as limiting in any way. Unless otherwise stated, all parts and percentages are given as a percentage by weight.

EXAMPLE I Blister Formation Study with Dichlorofluoroethane Sheets of a polystyrene with high impact resistance, characterized by a nominal flow rate of 2.6 grams per 10 minutes (measured according to Method D1238, Condition G of the American Society for the Testing of Materials), barrier layer structures Protective PS7100 were exposed to liquid dichlorodifluoroethane vapor (HCFC 141-6) at 35 ° C by sealing the leaf samples above the bottle opening. The sheet samples were prepared by compressing a lamination protective layer to the PS7100 to have a .058 millimeter layer in the PS7100 of 0.711 millimeter. The barrier layers of different compositions described in Table 1 were prepared by stirring with a single screw extrusion apparatus at 200 ° C. The effects of the diffusion of diclodifluoroethane through the specimens was monitored to determine the chemical attack. The time was recorded when the blistering occurred and the results are shown in Table 1. The adhesion of the protective barrier layers to the PS-7100 was evaluated by a hand peel resistance test. The results of the adhesion test are included in Table 1.

Table 1 Blister Formation Test with Diclodifluoroethane (Dichlorodifluoroethane vapor at 35 ° C). Leaf structure: 0.711 mm PS7100 volumetric layer, protective layer of .0508 mm.

Samples Composition Thickness of the Hours for Test Number of the layer protective layer form of protective millimeters blisters bond None (PS7100 of .762 millimeters only) 2-3 2 LM-6187 HDPE .0508 48-50 Deficient 3 Plexar PX209 .0508 150-160 Deficient 85% LM-6187 HDPE 0508 16-18 Regular 15% Stereon 840A 0254 85% Plexar PX209, 0508 94-96 Regular 15% Stereon 840A, 0254 43% LM-6187 HDPE, 0508 6-8 Good 42% PS5350 HIPS 15% Stereon 840A 43% Plexar PX209, 0508 16-18 Good 42% PS5350 HIPS 15% Stereon 840A 43% Plexar PX209, 0508 16-18 Good 42% PS5350 HIPS 15% FinaClear 520 50% Plexar PX209, 0508 22-26 Good 35% PS5350 HIPS 15% Stereon 840A Materials Plexar PX209: HDPE modified with maleic anhydride quantum, (modified polyolefin (i)) LM-6187: HDPE quantum with d = 0.96, MPI = 1.15. (polyolefone (iii)) PS5350: High impact polystyrene from BASF, (styrenic material based polymer (iv)) Stereon 840A: Triblock copolymer from Firestone S-B-S. (rubber (ii)) FinaClear 520: Thin triblock copolymer S-B-S. (rubber (ü)) Example 2 Rerrectified Compatibility Rectification compatibility of a protective layer was evaluated by testing the properties of the injection molded specimens of mixtures containing 15 percent of the protective layer, 83.5 percent of PS7100 and 1.5 percent of PS7800. The results Summarized in Table 2 they illustrated that the compositions of the protective layer provide excellent re-rectification compatibility. Even when the samples discussed below exhibit optimum re-rectifiability, it is expected that 0.3 to 3 percent additional rubber (iii) could be incorporated into the remaining samples in Table 1 to improve their re-corrected compatibility.

Table 2 Results of the Rerrectified Compatibility Study A B C D E F G PS7100 98 83.5 83.5 83.5 83.5 83.5 83.5 PS7800 2 1.5 1.5 1.5 1.5 1.5 1.5 Sample 7 - 15 - - - - - Sample 8 - - 15 - - - - Sample 9 - - - 15 - - - Sample 10 - - - - 15 15 - Sample 15 - - - - - - - Sample 16 - - - - - - 15 MFR (200.0 ° C, 5.0kg) 2.9 3.1 2.9 3.1 3.1 3.3 3.7 Vicat (0 ° C) 101 102 102 102 102 102 102 Limit of Tension (kg / cm2) 174.70 185.03 189.04 183.06 189.39 207.53 207.10 Break at Tension (kg / cm2) 261.59 265.29 277.33 262.78 275.93 282.89 378.39 Stretch Elongation (%) 54 75 77 74 68 68 63 Voltage Module (Kkg / cm2) 12.72 12.58 12.37 11.88 12.37 12.44 12.30 Izod Impact (Kilometers / meter) 11.42 15.23 14.69 13.60 14.14 13.06 13.06 Gardner (km) 2.63 2.33 > 3.68 2.35 3.59 2.79 2.42 Materials PS7100: BASF polystyrene with high impact resistance PS7800: BASF polystyrene with high impact resistance It should be understood that while the invention shown and described herein constitutes the preferred embodiment of the invention, it is not intended to illustrate all possible forms thereof. Various embodiments of the invention disclosed herein can be created by a person skilled in the art without deviating from the spirit and scope of the invention disclosed and claimed.

Claims (12)

R E I V I N D I C A C I O N E S:

1. A composition that is resistant to the action of polyurethane foam swelling agents, the composition comprises: (i) an effective amount of a polyethylene graft copolymer; and (ii) an effective amount of a block copolymer rubber and in addition (iii) a polyolefin and / or (iv) a styrene homopolymer or copolymer.

The composition according to claim 1, comprising: (i) from 1 to 70 parts by weight of a polyethylene graft copolymer; (ii) from 1 to 40 parts by weight of a block copolymer rubber; (iii) up to 90 parts by weight of a polyolefin selected from the group consisting of polyethylene, polypropylene, polybutylene and copolymers thereof, and / or (iv) up to 50 parts by weight of a styrene homopolymer or copolymer; wherein all parts by weight add up to the total weight of the composition.

3. The composition according to claim 1 or 2, comprising: (i) from 5 to 40 parts by weight of a polyethylene graft copolymer, (ii) from 5 to 30 parts by weight of a block copolymer rubber, (iii) from 20 to 80 parts by weight of a polyolefin; and (iv) from 0 to 48 parts by weight of a styrene homopolymer or copolymer; wherein all parts by weight add up to the total weight of the composition.

The composition of any of claims 1 to 3, wherein the polyethylene graft copolymer (i) results from the graft polymerization of a compound selected from the group consisting of unsaturated carboxylic acids, their functional derivatives and monomers containing vinyl and mixtures thereof to a polyethylene.

The composition of any of claims 1 to 4, wherein the polyethylene graft copolymer (i) results from the graft copolymerization of a compound selected from the group consisting of maleic anhydride, maleic acid, anhydride derivatives maleic, maleic acid derivatives and mixtures thereof to a polyethylene.

6. The composition of any of claims 1 to 5, wherein the block copolymer rubber (ii) is a synthetic block copolymer rubber which is selected from the group consisting of a styrene-butadiene diblock, a triblock of styrene- butylene styrene, a triblock of styrene-ethylene / butylene-styrene, a triblock of styrene-ethylene / butylene-styrene functionalized with maleic anhydride, maleic acid or mixtures thereof; or the mixtures thereof.

The composition of any of claims 1 to 6, wherein the polyolefin (iii) is a high density polyethylene (HDPE) having a density between 0.940 and 0.970 and a melt index of 1.00 to 1.30.

The composition of any of claims 1 to 7, wherein the styrene (iv) homopolymer or copolymer is a high impact resistance polystyrene (HIPS).

9. A barrier layer capable of protecting one or more of the action layers of the polyurethane foam swelling agents, the barrier layer comprises the composition of any one of claims 1 to 8.

10. A thermoformable compound comprising : (I) a functional layer comprising one or more sublayers of one or more polymers based on a styrenic material; and (II) a barrier layer according to claim 9 adhering to at least one surface of the functional layer.

11. The thermoformable compound according to claim 10, comprising: from 50 to 99 parts by weight of the functional layer (I); and from 1 to 50 parts by weight of the barrier layer (II); wherein all parts by weight are added to the total weight of the thermoformable compound.

12. An insulating cabinet wall structure comprising: (I) a functional layer comprising one or more sublayers of one or more polymers based on a styrenic material; and (II) a barrier layer according to claim 9, adhering to at least one surface of the functional layer; (III) an external structural wall; and (IV) an insulation adhered to both the barrier layer (II) (II) and the external structural wall (III) to be placed between them. SUMMARY OF THE INVENTION A composition for barrier layers for use in insulating cabinet wall structures, particularly those used in appliances such as refrigerators or dishwashing machines, is disclosed herein. The compositions of the barrier layer are resistant to the action of polyurethane foam swelling agents and have (i) an effective amount of a modified polyolefin, most preferably a polyethylene modified with a compound selected from the group which consists of maleic anhydride, maleic acid, maleic anhydride derivatives, maleic acid derivatives, and mixtures thereof; and (ii) an effective amount of a rubber. Optionally and especially preferably, the composition of the barrier layer may further contain (iii) an effective amount of a polyolefin which is selected from the group consisting of polyethylene, polypropylene, polybutylene and copolymers thereof. The invention further provides thermoformable compounds incorporating the barrier layer described above as well as insulating cabinet wall structures incorporating the thermoformable compound. Finally, the invention further provides a method for manufacturing a thermoformable composite incorporating the barrier layer of the invention.