CN105377933B

CN105377933B - Soft thermoplastic polyurethane elastomer and preparation method thereof

Info

Publication number: CN105377933B
Application number: CN201480038740.2A
Authority: CN
Inventors: D·尹; 宾-埃里克·陈; 野村晃; 林土典光
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2013-06-04
Filing date: 2014-05-28
Publication date: 2021-11-02
Anticipated expiration: 2034-05-28
Also published as: CN112876648A; KR102308489B1; CN112876648B; CN105377933A; KR20160018659A

Abstract

The invention discloses a thermoplastic polyurethane which is essentially free of plasticizers and has a Shore A hardness of 60 or less, which is prepared by polymerizing the following components in one step: i) a linear polyol, ii) an organic diisocyanate and iii) a glycol chain extender comprising primarily ethylene glycol and/or 1, 3-propanediol; wherein the linear polyol (i) has a number average molecular weight of 1.5X 10³g/mol to 5.0X 10³g/mol. The thermoplastic polyurethane of the present invention can be easily prepared by a conventional preparation method, and the thermoplastic polyurethane thus prepared can be molded into articles in a practical processing cycle. Furthermore, the thermoplastic polyurethane article has low shrinkage, has good low temperature characteristics and good mechanical characteristics, and is substantially not hardened at low temperatures.

Description

Soft thermoplastic polyurethane elastomer and preparation method thereof

Technical Field

The present invention relates to a one-step process for preparing a very soft thermoplastic polyurethane elastomer (TPU) which contains essentially no plasticizer and has a shore a hardness of 60 or less and which can be molded into TPU articles in the actual processing cycle.

Background

Thermoplastic polyurethane elastomers (TPU) have been known for a long time. They are industrially important because they combine the well-known advantages of good mechanical properties and inexpensive thermoplastic processability. A wide range of mechanical properties can be achieved by using various chemical building blocks. A review of TPUs, their properties and uses is described, for example, in Kunststoffe 68(1978), 819 or Kautschuk, Gummi, Kunststoffe 35(1982), 568.

TPUs are generally composed of polyols (usually polyester polyols or polyether polyols), diisocyanates (usually organic diisocyanates) and short-chain diols (chain extenders). The hardness of a TPU is primarily determined by the ratio of hard segments (formed by the reaction of the chain extender with the diisocyanate groups) to soft segments (formed by the reaction of the polyol with the diisocyanate groups). If the amount of hard segments is reduced such that the hardness of the TPU is reduced below the limit of 80 Shore A hardness, the resulting product is generally tacky, poorly curable, exhibits poor mold release in the injection molding process, and exhibits severe shrinkage. This TPU does not guarantee an economically acceptable number of injection molding cycles.

Currently, the soft TPU on the market is dominated by plasticized soft TPU. However, those plasticized TPUs exhibit a number of disadvantages. In the case of increasing the hardness of the composition to an undesirable level, the plasticizer may bloom or exude from the composition. The use of certain plasticizers has also been examined in terms of environment and toxicity. Thus, it is generally considered advantageous to eliminate the need for plasticizers in TPU compositions if the desired physical characteristics can be obtained without the need for plasticizers.

Another soft TPU is a soft TPU without plasticizer. However, products with a shore a hardness of less than 60 are almost not available on the market despite the high demand. The reason is that the process is too expensive or the mechanical properties of the TPU are not sufficient to be viable on the market.

US 8183330B2 discloses a soft, plasticizer-free TPU and a process for its preparation. The TPU has a shore a hardness of less than 75, preferably less than 70 and most preferably less than 65 and is substantially free and preferably free of plasticizers. It is made from starting materials comprising a hydroxyl terminated intermediate derived from a branched diol or comprising at least 2 different repeating units and contains 10 to 40 weight percent hard segments.

US 6790916B2 discloses a process for the preparation of a TPU having a shore a hardness of 45 to 65 and being easily demouldable. For this preparation, a complicated three-step process involving prepolymerization was employed.

EP 1932863A2 discloses a soft TPU and a process for its preparation. The TPU has a shore a hardness of 45 to 80 and good mold release properties. It is made in a single step reaction in which a branched polyester diol is used.

US 8138299B2 discloses a TPU without plasticizer and having a shore a hardness of 50 to 80. The TPU is made from a feedstock comprising two polyester diols, one polyester diol based on butane-1, 4-diol and at least one additional diol having at least 5 carbon atoms, and the other polyester diol based on butane-1, 4-diol and at least one additional diol having two or three carbon atoms.

Disclosure of Invention

It was therefore an object of the present invention to develop, using conventional preparation methods, soft TPU formulations having a shore a hardness of 60 or less, preferably from 55 to 30, even more preferably from 55 to 35, and which are substantially free of plasticizers. The shore a hardness was measured according to DIN 53505 as shown in the examples.

It is also an object of the present invention to provide the above described soft TPU which is substantially free of plasticizers and which can be molded by injection molding, extrusion or other molding methods in the actual processing cycle to give the finished product.

The inventors have surprisingly found that TPUs having a Shore A hardness of below 60 can be prepared in a one-step reaction from linear polyols, organic diisocyanatesAnd a glycol chain extender. Specifically, the one-shot process involves synthesizing the TPU by polymerizing the following components: i) a linear polyol, ii) an organic diisocyanate and iii) a glycol chain extender comprising mainly ethylene glycol and/or 1, 3-propylene glycol, wherein the linear polyol (i) has a number average molecular weight of 1.5 x 10³g/mol to 5.0X 10³g/mol.

It has also been found that the TPU thus prepared can be molded into TPU particles in the actual processing cycle. Although the TPU compositions of this invention are very soft in nature, they have the advantage that there is little tendency to adhere to the mold. Their use in injection molding applications is therefore very advantageous. In addition, the molded TPU article has good low temperature properties and good mechanical properties and does not substantially harden at low temperatures (e.g., below-10 ℃).

Detailed Description

In a first aspect, the present invention provides a one-step process for preparing a TPU, said TUP having a shore a hardness of 60 or less, preferably from 55 to 30, even more preferably from 50 to 35, said process comprising synthesizing the TPU by polymerizing: i) a linear polyol, ii) an organic diisocyanate and iii) a glycol chain extender comprising mainly ethylene glycol and/or 1, 3-propylene glycol, wherein the linear polyol (i) has a number average molecular weight of 1.5 x 10³g/mol to 5.0X 10³Within the range of (1).

The hard segment content in the formed TPU is from 5 to 14 weight percent, preferably from 6 to 12 weight percent, and even more preferably from 7 to 10 weight percent.

The linear polyol (i) used to prepare the TPU of this invention is selected from polyester polyols, polyether polyols, polycaprolactone polyols, polycarbonate polyols, and the like. Among them, polyester polyols and polyether polyols are preferred, and polyester polyols obtained from dicarboxylic acids and diols are more preferred.

The dicarboxylic acids used to prepare the polyester polyols include aliphatic dicarboxylic acids, cycloaliphatic dicarboxylic acids, aromatic dicarboxylic acids, or combinations thereof. Among them, aliphatic dicarboxylic acids are preferred. Suitable aliphatic dicarboxylic acids, which may be used alone or in mixtures, typically contain from 4 to 12 carbon atoms and include: succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, and the like. Adipic acid is the preferred acid.

The diols used to prepare the polyester polyols include aliphatic or aromatic diols, or combinations thereof, preferably aliphatic diols containing 2 to 8 carbon atoms and more preferably 2 to 6 carbon atoms. Some representative examples of aliphatic diols that can be used include ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, and the like.

In a preferred embodiment, only one aliphatic dicarboxylic acid is used to prepare the polyester polyol. In another preferred embodiment, one or two aliphatic diols are used to prepare the polyester polyol. Most preferably, the polyester polyol is obtained from adipic acid and 1, 3-propanediol (poly (1, 3-propylene adipate) diol, PPA), or from adipic acid and ethylene glycol and 1, 4-butanediol (poly (ethylene 1, 4-butylene adipate) diol, PEBA). In PEBA, the molar ratio of ethylene glycol to 1, 4-butanediol is preferably from 0.5:1 to 1.5:1, particularly preferably from 0.75:1 to 1.25: 1.

The number average molecular weight of the linear polyester polyol is usually 1.5X 10³g/mol to 5.0X 10³Within the range of (1). In a preferred embodiment, the linear polyol is a polyester polyol obtained from one aliphatic dicarboxylic acid and two aliphatic diols and has a number average molecular weight of 2.2 × 10³To 4.0X 10³And more preferably 2.5 × 10³To 3.5X 10³. In another preferred embodiment, the linear polyol is a polyester polyol obtained from an aliphatic dicarboxylic acid and an aliphatic diol and has a number average molecular weight of 1.5X 10³To 4.0X 10³And more preferably 1.8 × 10³To 3.5X 10³。

All molecular weights specified herein are in units of [ g/mol ], unless otherwise specified, and refer to number average molecular weight (Mn).

The organic diisocyanate (ii) used to prepare the TPU of this invention is an aliphatic diisocyanate or an aromatic diisocyanate. Aliphatic diisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate and/or octamethylene diisocyanate, 2-methylpentamethylene 1, 5-diisocyanate, 2-ethylbutylene 1, 4-diisocyanate, pentamethylene 1, 5-diisocyanate, butylene 1, 4-diisocyanate. Aromatic diisocyanates include diphenylmethane 2,2 '-diisocyanate, diphenylmethane 2, 4' -diisocyanate and/or diphenylmethane 4,4 '-diisocyanate (MDI), naphthylene 1, 5-diisocyanate (NDI), toluene 2, 4-diisocyanate and/or toluene 2, 6-diisocyanate (TDI), 3' -dimethyldiphenyl diisocyanate, 1, 2-diphenylethane diisocyanate and/or phenylene diisocyanate.

While aliphatic diisocyanates can be used, aromatic diisocyanates are highly preferred. In a particularly preferred embodiment, the organic diisocyanate is a diisocyanate comprising at least 90% by weight, more preferably at least 95% by weight, particularly preferably at least 99% by weight, of 4,4 '-diphenylmethane diisocyanate (4, 4' -MDI).

The glycol chain extender (iii) used to make the TPU of this invention is ethylene glycol or 1, 3-propylene glycol, or mixtures thereof. The glycol chain extender may contain, in addition to ethylene glycol and 1, 3-propanediol, small amounts of 1, 4-butanediol, 1, 5-pentanediol, and/or 1, 6-hexanediol, for example, in amounts of no more than 10 mole percent of the total moles of chain extender used. However, it is highly preferred to use only ethylene glycol and 1, 3-propanediol as chain extenders, and most preferably the chain extender is ethylene glycol.

In a particularly preferred embodiment, poly (1, 3-propylene adipate) glycol is used as component i), 4,4' -MDI is used as component ii) and ethylene glycol is used as component iii) to prepare the TPU of the invention, wherein the poly (1, 3-propylene adipate) glycol preferably has a number average molecular weight of more than 1.5X 10³And more preferably greater than 1.8X 10³. In another particularly preferred embodiment, poly (ethylene 1, 4-butylene adipate) glycol is used as component i), 4,4' -MDI is used as component ii) and ethylene glycol is used as component iii) to prepare the TPU of the invention, wherein the poly (ethylene 1, 4-butylene adipate) glycol preferably has a number average molecular weightThe amount is more than 2.2 × 10³And more preferably greater than 2.5X 10³。

In both of the above preferred embodiments, ethylene glycol is used as the chain extender in an amount of from 1.0 to 2.8 weight percent, preferably from 1.2 to 2.4 weight percent, and most preferably from 1.4 to 2.0 weight percent of the total weight of the TPU composition.

Conventional monofunctional compounds such as chain terminators or mold release aids may also be added in small amounts. Examples of suitable monofunctional compounds include alcohols (e.g., octanol and stearyl alcohol) and amines (e.g., butylamine and stearylamine).

It is often desirable to use catalysts such as stannous or other metal carboxylates and tertiary amines. Examples of metal carboxylate catalysts include stannous octoate, dibutyltin dilaurate, phenyl mercuric propionate, lead octoate, iron acetylacetonate, magnesium acetylacetonate, and the like. Examples of tertiary amine catalysts include triethylenediamine and the like. The amount of the one or more catalysts is relatively low, typically from about 10 to about 100 parts by weight per million parts by weight of the final TPU polymer formed.

In addition to the TPU components and the catalysts, it is also possible to add the customary auxiliaries and/or additives. Some examples which may be mentioned include lubricants and mould release agents, flame retardants, nucleating agents, oxidation stabilizers, hydrolysis stabilizers, dyes and pigments, inorganic and/or organic fillers and reinforcing agents. In a preferred embodiment, lubricants such as fatty acid esters and/or fatty acid amides are used. In another preferred embodiment, hydrolysis stabilizers such as oligomeric aliphatic or aromatic carbodiimides and/or polymeric aliphatic or aromatic carbodiimides are used. Herein, "substantially free of plasticizer" means that the amount of plasticizer can optionally be less than 5 weight percent of the total weight of the TPU composition. However, in a further preferred embodiment, no plasticizer is used. Antioxidants can be added if the TPU of the invention is thermally oxidatively damaged during its use, with phenolic antioxidants being preferred. Auxiliaries and/or additives can be added in the reaction to form the TPU or in the second synthesis step.

To prepare the TPU, the constituent components may be reacted in amounts such that the equivalent molar ratio of NCO groups to the sum of NCO-reactive groups (particularly the chain extender and OH groups in the polyol) is from 0.9:1.0 to 1.1:1.0, preferably from 0.95:1.0 to 1.05:1.0, and more preferably from 0.97:1.0 to 1.03: 1.0.

The TPUs of the invention may be prepared continuously or batchwise. The most well known industrial processes for preparing TPUs are the belt process and the extruder process. In this process, components i), ii) and iii) may be added simultaneously or in any order. In a preferred embodiment, component i) is premixed with component iii) and fed to the reactor as a blend, and component ii) is added separately to the reactor. During polymerization, the reaction temperature is generally controlled in the range of from about 100 ℃ to about 300 ℃, preferably from about 150 ℃ to about 230 ℃. The TPU thus prepared is cooled and granulated. Granulation may be carried out by any granulation method known in the art.

In a second aspect of the invention, there is provided a TPU made by the above process having a shore a hardness of 60 or less, preferably from 55 to 30, and more preferably from 50 to 35.

In a third aspect of the invention, a process for making a molded article using the TPU prepared by the above process is provided. For example, injection molding, extrusion, calendering, or blow molding can be used to prepare the molded article, and injection molding is preferred. The process for preparing a molded article by injection molding using the TPU comprises: (a) heating the TPU to a temperature above its melting point; (b) injecting the molten TPU into a mold; (c) cooling the TPU in the mold to a temperature below its solidification temperature to produce a molded article; and (d) removing the molded article from the mold. During the injection molding process, TPU solidifies rapidly and is therefore easily removed from the mold.

The TPUs of the invention have good mechanical properties. The TPUs of the invention have good elastomeric properties even at low temperatures (i.e.no crystallization of the soft segment), which is manifested in a smaller increase in hardness after a period of time at temperatures below 0 ℃ or even below-10 ℃.

The present invention is illustrated by the following examples, which are for illustrative purposes only and are not to be construed as limiting the scope of the invention or the manner in which it is practiced.

Examples

The following methods and criteria were used for the determination and evaluation of each parameter.

Hardness of shore A

The shore a hardness was measured according to DIN 53505, wherein the hardness values were read 3 seconds after contacting the pressure foot with the test specimen. Hereinafter, the hardness is expressed as shore a hardness (3 seconds).

Tensile strength

Tensile strength was determined according to DIN 53504, using a S2 test bar.

Elongation at break

The elongation at break was determined according to DIN 53504, using a S2 test bar.

Amount of wear

The amount of wear was determined in accordance with DIN 53516.

After demolding, all test specimens were annealed at 100 ℃ for 20 hours, then conditioned at 23 ℃ for at least 16 hours prior to testing.

The hardness increase at low temperature was determined as the hardness increase of the above annealed test specimens after 48 hours of treatment at low temperature of-30 ℃ and subsequent 24 hours of conditioning at 23 ℃. If the increase in Shore A hardness is less than 5, it is defined as the test sample having a low increase in hardness at low temperatures.

Example 1

229.18g of 4,4' -MDI, 35.18g of ethylene glycol and 1000g of a number-average molar mass of 3.0X 10 obtained from adipic acid and ethylene glycol and 1, 4-butanediol³The g/mol polyester Polyol (PEBA) is processed in a reaction extruder to synthesize TPU, wherein the molar ratio of ethylene glycol to 1, 4-butanediol is 1:1. In addition, 8g of hydrolysis stabilizer (oligomeric carbodiimide obtained from tetramethylxylene diisocyanate (TMXDI), e.g.Elastostab H01 from BASF), 2.54g of antioxidant (hindered phenol obtained from tetramethylxylene and polyethylene glycol, e.g.Irganox 1010 from BASF) and 3.82g of lubricant (ester wax based on montanic acid, e.g.Licowax E from Clariant) were added. The TPU granules prepared are converted by injection moulding intoThe samples were tested.

Example 2

184.15g of 4,4' -MDI, 24.01g of ethylene glycol and 1000g of a number-average molar mass of 3.0X 10 obtained from adipic acid and ethylene glycol and 1, 4-butanediol³The g/mol polyester Polyol (PEBA) is processed in a reaction extruder to synthesize TPU, wherein the molar ratio of ethylene glycol to 1, 4-butanediol is 1:1. In addition, 8g of hydrolysis stabilizer (oligomeric carbodiimide obtained from TMXDI, e.g.Elastostab H01 from BASF), 2.43g of antioxidant (hindered phenol obtained from tetramethylxylene and polyethylene glycol, e.g.Irganox 1010 from BASF) and 6.08g of lubricant (ester wax based on montanic acid, e.g.Licowax E from Clariant) were added. The prepared TPU granules were converted into test specimens by injection molding.

Example 3

163g of 4,4' -MDI, 18.79g of ethylene glycol and 1000g of a number average molar mass of 3.0X 10 obtained from adipic acid and ethylene glycol and 1, 4-butanediol³The g/mol polyester Polyol (PEBA) is processed in a reaction extruder to synthesize TPU, wherein the molar ratio of ethylene glycol to 1, 4-butanediol is 1:1. In addition, 8g of hydrolysis stabilizer (oligomeric carbodiimide obtained from TMXDI, e.g.Elastostab H01 from BASF), 2.38g of antioxidant (hindered phenol obtained from tetramethylxylene and polyethylene glycol, e.g.Irganox 1010 from BASF) and 5.95g of lubricant (ester wax based on montanic acid, e.g.Licowax E from Clariant) were added. The prepared TPU granules were converted into test specimens by injection molding.

The results of mechanical testing of the samples prepared in examples 1 to 3 are shown in table 1.

TABLE 1

The samples prepared by examples 1 to 3 can be easily taken out of the mold during processing by injection molding. As can be seen from table 1, they all show a shore a hardness (3 seconds) of less than 60, and satisfactory mechanical properties. Furthermore, they all show a low hardness increase after storage at low temperatures.

Example 4

276.33g of 4,4' -MDI, 36.53g of ethylene glycol and 1000g of a number-average molar mass of 2.0X 10 obtained from adipic acid and 1, 3-propanediol³The g/mol of Polyester Polyol (PPA) is processed in a reaction extruder to synthesize the TPU. In addition, 8g of hydrolysis stabilizer (oligomeric carbodiimide obtained from TMXDI, e.g.Elastostab H01 from BASF), 2.64g of antioxidant (hindered phenol obtained from tetramethylxylene and polyethylene glycol, e.g.Irganox 1010 from BASF) and 3.96g of lubricant (ester wax based on montanic acid, e.g.Licowax E from Clariant) were added. The prepared TPU granules were converted into test specimens by injection molding.

Example 5

229.53g of 4,4' -MDI, 24.93g of ethylene glycol and 1000g of a number-average molar mass of 2.0X 10 obtained from adipic acid and 1, 3-propanediol³The g/mol of Polyester Polyol (PPA) is processed in a reaction extruder to synthesize the TPU. In addition, 8g of hydrolysis stabilizer (oligomeric carbodiimide obtained from TMXDI, e.g.Elastostab H01 from BASF), 2.53g of antioxidant (hindered phenol obtained from tetramethylxylene and polyethylene glycol, e.g.Irganox 1010 from BASF) and 6.31g of lubricant (ester wax based on montanic acid, e.g.Licowax E from Clariant) were added. The prepared TPU granules were converted into test specimens by injection molding.

Example 6

207.72g of 4,4' -MDI, 19.51g of ethylene glycol and 1000g of a number-average molar mass of 2.0X 10 obtained from adipic acid and 1, 3-propanediol³The g/mol of Polyester Polyol (PPA) is processed in a reaction extruder to synthesize the TPU. In addition, 8g of hydrolysis stabilizer (oligomeric carbodiimide obtained from TMXDI, e.g.Elastostab H01 from BASF), 2.47g of antioxidant (hindered phenol obtained from tetramethylxylene and polyethylene glycol, e.g.Irganox 1010 from BASF) and 6.18g of lubricant (ester wax based on montanic acid, e.g.Licowax E from Clariant) were added. The prepared TPU granules were converted into test specimens by injection molding.

The results of mechanical testing of the samples prepared in examples 4 to 6 are shown in table 2.

TABLE 2

The samples prepared by examples 4 to 6 can be easily taken out of the mold during processing by injection molding. As can be seen from table 2, they all show a shore a hardness (3 seconds) of less than 60, and satisfactory mechanical properties. Furthermore, they all show a low hardness increase after storage at low temperatures.

Claims

1. A thermoplastic polyurethane which does not contain a plasticizer and has a shore a hardness of 60 or less, measured according to DIN 53505, wherein the hardness value is read 3 seconds after contacting a pressure foot with a test sample and the thermoplastic polyurethane is prepared by a one-step reaction of: i) a linear polyol, ii) an organic diisocyanate and iii) a glycol chain extender, wherein the glycol chain extender is ethylene glycol, and optionally 1, 4-butanediol, 1, 5-pentanediol and/or 1, 6-hexanediol, the amount of the 1, 4-butanediol, 1, 5-pentanediol and/or 1, 6-hexanediol being no more than 10 mole% of the total number of moles of the glycol chain extender, wherein the linear polyol (i) is obtained from adipic acid and 1, 3-propanediol and has a number average molecular weight of 1.8 x 10³g/mol to 3.5X 10³Poly (1, 3-propylene adipate) glycol in the range of g/mol.

2. The thermoplastic polyurethane of claim 1, wherein the thermoplastic polyurethane has a shore a hardness of 55 to 30, measured according to DIN 53505, wherein the hardness value is read 3 seconds after contacting the pressure foot with the test sample.

3. The thermoplastic polyurethane according to claim 2, wherein the thermoplastic polyurethane has a Shore A hardness of from 50 to 35 measured according to DIN 53505, wherein the hardness value is read 3 seconds after contacting the pressure foot with the test sample.

4. The thermoplastic polyurethane specified in claim 1 wherein the organic diisocyanate is an aromatic diisocyanate.

5. The thermoplastic polyurethane specified in claim 4 wherein the organic diisocyanate is diphenylmethane diisocyanate.

6. The thermoplastic polyurethane specified in claim 5 wherein the organic diisocyanate is 4,4' -diphenylmethane diisocyanate.

7. The thermoplastic polyurethane specified in claim 1 wherein the glycol chain extender is ethylene glycol.

8. The thermoplastic polyurethane specified in claim 1 wherein the glycol chain extender is ethylene glycol; wherein the organic diisocyanate is 4,4' -diphenylmethane diisocyanate; and wherein the linear polyol is a poly (1, 3-propylene adipate) glycol obtained from adipic acid and 1, 3-propanediol and has a number average molecular weight of 1.8 x 10³To 3.5X 10³。

9. The thermoplastic polyurethane according to any of claims 7 to 8, wherein ethylene glycol is used as chain extender in an amount of from 1.0 to 2.8% by weight based on the total weight of the thermoplastic polyurethane.

10. The thermoplastic polyurethane of claim 9 wherein the amount of ethylene glycol is from 1.2 to 2.4 weight percent of the total weight of the thermoplastic polyurethane.

11. The thermoplastic polyurethane specified in claim 10 wherein the amount of ethylene glycol used is from 1.4 to 2.0 weight percent of the total weight of the thermoplastic polyurethane.

12. A process for producing a molded article of thermoplastic polyurethane, which comprises molding the thermoplastic polyurethane according to any one of claims 1 to 11 by injection molding or extrusion.