Polyurethane Composites
Technical field
The present invention relates to a polyurethane composition, a polyurethane composite comprising said polyurethane composition and a reinforced material, and an article produced from said polyurethane composite.
Background of art
Polyurethane (PU) composites are nowadays used in many applications because of their broad properties. Particularly, polyurethane composites exhibit excellent performance and unique advantages in pultrusion process compared with the traditional structure materials such as concrete, steel, aluminum, and conventional thermosetting resins.
The pultrusion process is a continuous process for producing fiber-reinforced profiles, wherein the fibers are impregnated by polyurethane composition in an open bath or in a closed injection box, and then shaped and hardened. Although polyurethane has various advantages, its relatively short processing time makes it challenging to produce large size parts by pultrusion process, such as bridge components, large artificial wood, large pole structure, complex window profile, reefer container, etc.
CN104045806A discloses a polyurethane composition for preparing a polyurethane com- posite, comprising: a) a polyisocyanate component, wherein the polyisocyanate component comprises 2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate; and b) an isocyanate reactive component.
US2013/0309924A1 discloses a reinforced pultruded polyurethane obtainable via reacting A) polyether polyols, B) epoxides with C) organic polyisocyanates.
US8,663,414B2 discloses a pultrusion resin system, comprising a) a di- or polyisocyanate, b) a compound having at least two groups reactive toward an isocyanate, c) a catalyst, d) a polybasic acid having a functionality greater than or equal to 2 and, optionally, e) a further auxiliary or additive, where a boiling point of the polybasic acid is at least 200°C at standard pressure and the polybasic acid is soluble in the compound having at least two groups reactive toward an isocyanate.
However, there is still a need to find a polyurethane composition having relatively long processing time to allow the production of larger size parts.
Invention summary
Thus, the present invention provides a polyurethane composition, comprising
(1 ) an isocyanate; and
(2) an isocyanate reactive compound;
wherein the isocyanate comprises 2,2'-diphenylmethane diisocyanate (2,2'-MDI) and 2,4'- diphenylmethane diisocyanate (2,4'-MDI), and the amount of 2,2'-diphenylmethane diisocyanate is in the range of 10-100wt% based on the total weight of 2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate.
The present invention provides a polyurethane composite, comprising:
(1 ) a polyurethane composition above; and
(2) a reinforcing material.
The present invention also provides an article produced from said polyurethane composite above.
The polyurethane compositions of the present invention have prolonged gel time such that the polyurethane compositions are particularly suitable for producing large size parts such as bridge components, large artificial wood, large pole structure, complex window profile, reefer container, etc.
Embodiments
In one embodiment of the invention, a polyurethane composition is provided, wherein the polyurethane composition comprises: (1 ) an isocyanate; and (2) an isocyanate reactive compound; wherein the isocyanate comprises 2,2'-diphenylmethane diisocyanate and 2,4'- diphenylmethane diisocyanate, and the amount of 2,2'-diphenylmethane diisocyanate is in the range of 10-100wt%, preferably 15-70wt%, more preferably 20-50wt%, still more preferably 20- 30wt% based on the total weight of 2,2'-diphenylmethane diisocyanate and 2,4'- diphenylmethane diisocyanate.
In the polyurethane composition, the total amount of 2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate is in the range of 50-100wt%, preferably 60-90wt%, more preferably 60-80wt% based on the total weight of the isocyanate.
The polyurethane composition can be compact or foam. In one embodiment of the invention, the polyurethane composition has a free rise density of from 30g/l to 900g/l.
The isocyanate can comprise the mixtures of monomeric diphenylmethane diisocyanates and of diphenylmethane diisocyanate homologs having a greater number of rings (polymeric MDI), tolylene diisocyanate (TDI), for example tolylene diisoyanate isomers such as tolylene 2,4- or 2,6-diisocyanate, or a mixture of these, naphthylene diisocyanate (NDI), or a mixture thereof, preferably 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'- diphenylmethane diisocyanate (4,4'-MDI), polymeric MDI, or combination thereof.
The isocyanate reactive compound, also termed "polyols" for the purposes of this invention, can comprise any of the compounds having at least two groups reactive toward isocyanates, examples being OH, SH, NH, Nhb, -COON, and CH-acidic groups.
Isocyanate reactive compounds are known to the person skilled in the art and are described by way of example in "Kunststoffhandbuch, 7, Polyurethane" [Plastics Handbook, 7, Po- lyurethanes] Carl Hanser-Verlag, 3rd edition, 1993, chapter 3.1 . Examples of the isocyanate reactive compounds are polyetherols or polyesterols. The isocyanate reactive compounds can be polyetherols or polyesterols comprising secondary OH groups, an example being polypropylene oxide. The functionality of these polyetherols or polyesterols is preferably from 2 to 4, particularly preferably from 2 to 3.
It is usual to use polyetherols and/or polyesterols having from 2 to 8 hydrogen atoms reactive toward isocyanate, and to use low-molecular-weight polyols, such as glycerol, dipropylene glycol, and/or tripropylene glycol. The OH number of these compounds is usually in the range from 30 to 2000 mg KOH/g, preferably in the range from 40 to 1000 mg KOH/g. The average OH number of all of the isocyanate reactive compound used here having at least two groups reactive toward isocyanates is from 100 to 1000 mg KOH/g, preferably from 300 to 900 mg KOH/g.
The polyetherols are obtained by known processes, for example via anionic polymerization of alkylene oxides with addition of at least one starter molecule comprising from 2 to 8, preferably from 2 to 6, and particularly preferably from 2 to 4, reactive hydrogen atoms, in the presence of catalysts. Catalysts used can comprise alkali metal hydroxides, such as sodium hydroxide or potassium hydroxide, or alkali metal alcoholates, such as sodium methoxide, sodi- urn ethoxide, potassium ethoxide, or potassium isopropoxide, or, in the case of cationic polymerization, Lewis acids, such as antimony pentachloride, boron trifluoride etherate, or bleaching earth. Other catalysts that can be used are double-metal cyanide compounds, known as DMC catalysts.
The alkylene oxides used preferably comprise one or more compounds having from 2 to 4 carbon atoms in the alkylene moiety, e.g. tetrahydrofuran, ethylene oxide, propylene 1 ,2-oxide, butylene 1 ,2-oxide or butylene 2,3-oxide, in each case alone or in the form of a mixture, and preferably propylene 1 ,2-oxide and/or ethylene oxide, in particular propylene 1 ,2-oxide.
Examples of starter molecules that can be used are ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, pentaerythritol, sugar derivatives, such as sucrose, hexitol derivati- ves, such as sorbitol, methylamine, ethylamine, isopropylamine, butylamine, benzylamine, aniline, toluidine, toluenediamine, naphthylamine, ethylenediamine, diethylenetriamine, 4,4'- methylenedianiline, 1 ,3-propanediamine, 1 ,6-hexanediamine, ethanolamine, diethanolamine, triethanolamine, and also other di- or polyhydric alcohols, or di- or polybasic amines.
The polyester alcohols used are mostly produced via condensation of polyhydric alcohols having from 2 to 12 carbon atoms, e.g. ethylene glycol, diethylene glycol, butanediol, trimethylolpropane, glycerol, or pentaerythritol, with polybasic carboxylic acids having from 2 to 12 car-
bon atoms, e.g. succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, and the isomers of naphthalenedicarboxylic acids, or their anhydrides.
Other starting materials that can also be used concomitantly in producing the polyesters are hydrophobic substances. The hydrophobic substances are substances insoluble in water which comprise a nonpolar organic moiety, and which also have at least one reactive group selected from hydroxy, carboxylic acid, carboxylic ester, or a mixture thereof. The equivalent weight of the hydrophobic materials is preferably from 130 to 1000 g/mol. Examples of materials that can be used are fatty acids, such as stearic acid, oleic acid, palmitic acid, lauric acid, or linoleic acid, and also fats and oils, e.g. castor oil, maize oil, sunflower oil, soybean oil, coconut oil, olive oil, or tall oil. If polyesters comprise hydrophobic substances, the proportion of the hydrophobic substances, based on the total monomer content of the polyester alcohol, is preferably from 1 to 30 mol %, particularly preferably from 4 to 15 mol %.
The functionality of the polyesterols used is preferably from 1.5 to 5, particularly preferably from 1.8 to 3.5.
In one particularly preferred embodiment, the isocyanate-reactive compounds comprise po- lyetherols, in particular exclusively polyetherols. The actual average functionality of the po- lyetherols is preferably from 2 to 4, particularly preferably from 2.5 to 3.5, in particular from 2.8 to 3.2, and their OH number is preferably from 300 to 900 mg KOH/g, and their content of se- condary OH groups is preferably at least 50%, with preference at least 60%, with particular preference at least 70% and in particular at least 80%. The polyetherol used here preferably comprises polyetherol based on glycerol as starter and on propylene-1 ,2-oxide.
The polyurethane composition can further comprise additives. Said additives can comprise any of the auxiliaries and additives known for producing polyurethanes. Examples that may be mentioned are surfactant, release agents, coupling agents, fillers, dyes, pigments, flame retar- dants, hydrolysis stabilizers, viscosity reducers, water scavengers, antifoaming agents, and also substances having fungistatic and bacteriostatic action. Substances of this type are known and are described by way of example in "Kunststoffhandbuch, Band 7, Polyurethane" [Plastics Handbook, volume 7, Polyurethanes] Carl Hanser Verlag, 3rd edition 1993, chapter 3.4.4 and 3.4.6 to 3.4.1 1 .
Examples of viscosity reducers that can be used are y-butyrolactone, propylene carbonate, and also reactive diluents, such as dipropylene glycol, diethylene glycol, and tripropylene glycol.
Coupling agents that can be used comprise silanes, such as isocyanate silanes, epoxysila- nes, or aminosilanes. Substances of this type are described by way of example in E. P. Plued-
demann, Silane Coupling Agents, 2nd ed., Plenum Press, New York, 1991 and in K. L. Mittal, ed., Silanes and Other Coupling Agents, VSP, Utrecht, 1992.
Release agents that can be used are any of the conventional release agents used in producing polyurethanes, examples being long-chain carboxylic acids, in particular fatty acids, such as stearic acid, amines of long-chain carboxylic acids, e.g. stearamide, fatty acid esters, metal salts of long-chain carboxylic acids, e.g. zinc stearate, or silicones. Particularly suitable materials are the internal release agents obtainable specifically for the pultrusion process, e.g. from Axel Plastics or Technick Products. The internal release agents from Technick Products probably comprise phosphoric acid and fatty acids. The internal release agents from Axel Plastics probably comprise fatty acids.
In one embodiment of the present invention, the molar ratio of the isocyanate reactive compound to the isocyanate is in the range of 1 :0.5 to 1 :2.
Polyurethane composites are also provided, wherein the polyurethane composite comprises:
(1 ) a polyurethane composition above; and
(2) a reinforcing material.
Preferably, the reinforcing material is a fiber material. The fiber material used can comprise any of the types of continuous-filament fibers. Continuous-filament fiber here means a fiber material the length of which is at least a plurality of meters. These materials are by way of example unwound from rolls. The fiber material used here can comprise individual fibers, known as fiber rovings, braided fibers, fiber mats, fiber scrims, and woven fibers. Particularly in the case of fiber composites, such as braided fibers, twisted fibers, fiber scrims, or woven fibers, there can also be shorter individual fibers comprised within the individual fibers comprised within said fiber structures. It is preferable that the fiber material comprises or is composed of glass fiber, glass mats, carbon fiber, polyester fiber, natural fiber, aramid fiber, basalt fiber, or nylon fiber, and it is particularly preferable to use carbon fibers or glass fibers.
In one embodiment of the present invention, the weight ratio of the polyurethane composition to the reinforcing material is in the range of 10:90 to 70:30, preferably 15:85 to 50:50, more preferably 18:82 to 30:70.
In general, the polyurethane composites are prepared by mixing components of the polyurethane composition to give a polyurethane reaction mixture, and then impregnating the reinforcing material with the resultant reaction mixture.
The present invention also provides an article produced from a polyurethane composite above by pultrusion.
In one embodiment of the present invention, the articles are bridge components, large artificial wood, large pole structure, complex window profile, reefer container.
Examples
The present invention is now further illustrated by reference to the following examples, however, the examples are used for the purpose of explanation and not intended to limit the scopes of the present invention.
All materials used in the examples are available in the market, and their amounts used are listed in Table 1 .
Comparative example 1
Component A and component B are mixed for 1 min using SpeedMixer available from FlackTek Inc. at 25°C. Then, gel time is measured by gel timer available from SHYODU IN- STRU ME NT COMPANY.
In addition, PU panel sample is prepared by mixing component A and component B for 1 min using SpeedMixer at 25°C, and vacuum pumping for 7 min at 70°C and placing for 8 min at 70°C, then curing for 1 h at 150°C.
Comparative example 2
Comparative example 2 are carried out by same procedure as comparative example 1 except that the amounts of 2,2'-MDI and 2,4'-MDI and their ratio vary.
Examples 1 -5
Examples 1 -5 are carried out by same procedure as comparative example 1 according to the components and amounts listed in Table 1 .
The pure PU resin's mechanical properties of Comparative example 1 , Examples 1 -3 are listed in Table 2. The preparation of PU panel sample can be referred to Comparative example 1 .
In addition, glass fiber reinforced PU composite is prepared using a mixture of glass fiber and sample from Example 1 by pultrusion process, wherein the content of glass fiber is 80wt% based on the weight of the PU composite. The measured result is shown in Table 3.
Table 1 : Components and properties of polyurethane composition
Table 1 shows that the gel times of Example 1 -3 are significantly greater than that of Comparative example 1 and Comparative example 2, even about 2 times or above of the gel time of Comparative example 1 and Comparative example 2, which indicates that appropriate amount of 2,2'-MDI based on the total amount of 2,2'-MDI and 2,4'-MDI used is important to prolong the processing time. Furthermore, the prolonging of the gel time does not compromise its curing speed. Example 1 , Example 4 and Example 5 show that the gel times become longer with the ratio of 2,2'-MDI/2,4'-MDI increasing even if the total amount of 2,2'-MDI and 2,4'-MDI is about same.
Physical properties of PU panel samples prepared from polyurethane compositions are measured as shown in table 2.
Table 2: Physical properties of PU panel samples
In Table 2, the physical performances of PU panel samples of Example 1 -3 are comparable to Comparative example 1 , which indicates that the prolonging of the gel time does not compromise its physical performances.
Table 3: Physical properties of PU composite samples prepared via pultrusion
PU composite samples are prepared via pultrusion process by impregnating glass fiber (Owens Corning PS4100) with sample of example 1. The physical properties of the PU composites are excellent, as shown in Table 3, which are particularly suitable for producing large size composite parts, e.g. bridge components, large artificial wood, large pole structure, complex window profile, reefer container.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the present invention. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents.