JPH0135006B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a urethane elastomer that has excellent heat resistance and a high elastic modulus, and more specifically, a highly productive RIM that has a high flexural modulus and a low temperature index that have not been obtained with conventional urethane elastomers.
The present invention relates to a urethane elastomer suitable for (Reaction Injection Molding). Conventional urethane elastomers for RIM with excellent flexural modulus include ethylene glycol, diethylene glycol, propylene glycol, or 1,4-
An elastomer obtained by mixing a low molecular weight hydroxy compound having two active hydrogen atoms at the molecular end, such as butanediol, as a chain extender and reacting the mixture with an aromatic polyisocyanate has been used. However, even if the flexural modulus of such polyurethane elastomers is excellent, it is at best
It is approximately 5000Kg/cm ² or less, and its uses are limited to automobile bumpers, pine guards, side shields, etc. Generally speaking, in the case of urethane elastomers, in order to improve the flexural modulus, a large amount of a low molecular weight hydroxy compound with a molecular weight of about 200 or less, such as ethylene glycol, is blended in to achieve this objective. In this method, the compatibility between the high molecular weight polyol and the low molecular weight hydroxy compound is extremely poor and it is difficult to maintain a homogeneous stock solution state. Further, since the brittleness of the obtained elastomer increases, it is difficult to obtain sufficient green strength (for example, bending strength during demolding), so that productivity cannot be improved. Other methods for improving the flexural modulus include using ethylene glycol, 1,4-butanediol, and other low-molecular-weight hydroxyl compounds with two active hydrogen atoms at the molecular ends, for example, for high-molecular-weight polyoxyalkylene polyols or graft copolymer polyols. There is a method of mixing a compound and an alkylene oxide addition polyol of aniline (for example, "KA-500" manufactured by Mitsui Nisso Urethane Co., Ltd.) as an auxiliary crosslinking agent, and reacting the mixture with an aromatic polyisocyanate. It is thought that the crosslinking agent improves the compatibility between the low molecular weight hydroxy compound and the high molecular weight polyol, and it is possible to incorporate a large amount of the low molecular weight hydroxy compound, and the elastic modulus of the resulting elastomer can reach 10,000 kg/ ^cm2 . be.
However, this elastomer has the drawbacks of poor heat resistance and a large temperature index (temperature dependence) of the elastic modulus. This type of high modulus elastomer is used for the exterior panels of automobile fenders, etc., but painting is essential, and the lack of heat resistance, which causes deformation of the product during baking in the painting process, is a fatal drawback. The present invention eliminates these conventional drawbacks, and by including a specific polyester polyol as a polyol component, the microscopic structure of the urethane elastomer is made more homogeneous, and furthermore, the microscopic structure of the urethane elastomer is made more homogeneous. The present invention provides a urethane elastomer that has a high elastic modulus and excellent heat resistance because it is mixed in the molecular state, and has a low temperature dependence of the elastic modulus, and is suitable for high-productivity RIM. That is, the present invention provides: (1) A high molecular weight polymer obtained by graft polymerization of a vinyl compound mainly composed of styrene acrylonitrile, the number of functional groups thereof is 2.1 to 3, and the average molecular weight is 2000 to 8000. 100 parts by weight of polyol, (2) having at least 30% by weight of phthalic acid residues and at least 2 hydroxyl groups and an average molecular weight of 300 to 2000;
about 10 to 40 parts by weight of a polyester polyol, (3) 25 to 50 parts by weight of a chain extender having a molecular weight of 400 or more, and (4) polyisocyanate so that the NCO index is about 1.05 to 1.15, and as necessary. The present invention relates to a method for producing a heat-resistant, high-modulus urethane elastomer having a flexural modulus of 5000 (Kg/cm ² ) or more at room temperature, which is characterized in that the reaction is carried out in the presence of a repellent foaming agent. The graft polymer polyol used in the present invention is a polymer polyol obtained by graft polymerizing a vinyl compound mainly composed of styrene/acrylonitrile to a polyether polyol or a polyester polyol. In the above, acrylonitrile may be replaced with methyl acrylate or methyl methacrylate within 10% by weight. Examples of the polyols include polyether polyols such as polyoxyethylene glycol, polyoxypropylene glycol, polyoxypropylene/oxyethylene glycol, and polyoxybutylene glycol, and polyester polyols. The number of functional groups of such a graft polymer polyol is preferably 2 to 3, and the average molecular weight is
2000-8000 is preferred. In the case of a polyol with a molecular weight of less than 2000, the physical properties of the produced elastomer, especially the temperature index of the elastic modulus, will be significantly worse (larger).
There is also a decrease in impact resistance. Also, the molecular weight
If it exceeds 8,000, the molecular weight is too high and its reactivity decreases, resulting in a disadvantage that the balance of reactivity with other components is lost. The polyol of the present invention preferably has about 20 to 100% of its terminal groups converted into primary OH to increase its reactivity. The polyester polyol used in the present invention contains at least 30% by weight, preferably at least 50% by weight, of phthalic acid residues, with 2 to 8, preferably 2
~Has 5 hydroxyl groups, average molecular weight ~300
2000, preferably 500 to 1500 polyhydroxy compounds. Such polyester polyols are, for example, polyvalent, preferably divalent, optionally 3 to 5
It is the reaction product of a hydric alcohol with phthalic acid and optionally other polybasic, preferably dibasic, carboxylic acids. Instead of using free phthalic acid and polycarboxylic acid, the corresponding acid anhydrides or the corresponding acid esters of lower alcohols may be used in the production of polyester polyols.
Orthophthalic acid, isophthalic acid, and terephthalic acid can be used as the phthalic acid. Other optional carboxylic acids may be aliphatic, cycloaliphatic, aromatic, such as adipic acid, succinic acid, azelaic acid, maleic acid, maleic anhydride, fumaric acid, sebacic acid, etc. can give. Suitable polyhydric alcohols are aliphatic, cycloaliphatic, heterocyclic, aromatic compounds having at least two hydroxyl groups, such as ethylene glycol, propylene glycol, diethylene glycol, 1,4-
Butanediol, 1,3-butanediol, 1,
6-hexanediol, glycerin, trimethylolpropane, pentaerythritol, neopentyl glycol, mannitol, sorbitol,
Examples include glucose, sucrose, 4,4'-dihydroxydiphenylpropane, and the like. Further, as the polyhydric alcohol, polyols such as polyoxypropylene glycol, polyoxyethylene glycol, and polyoxybutylene glycol can also be used. Lactones such as ε-caprolactone or hydroxycarboxylic acids such as ω-hydroxycaproic acid can also be used as starting materials. If the molecular weight of the polyester polyol is less than 300, the impact resistance will decrease and the temperature dependence of the elastic modulus will increase.
When the molecular weight exceeds 2000, compatibility with other components decreases. If the phthalate residue content is less than 30%,
Heat resistance deteriorates and elastic modulus also decreases. As the chain extender used in the present invention, ethylene glycol and/or 1,4 butanediol are suitable. Optionally, a compound containing at least two OH groups having a molecular weight of 400 or less can be used mixed with ethylene glycol and/or 1,4-butanediol. The above compounds include 1,3-butanediol, diethylene glycol, propylene glycol, dipropylene glycol, 1,6-hexanediol, 4,4'-dihydroxydiphenylpropane, glycerin, trimethylolpropane, triethanolamine,
Examples include pentaerythritol, sorbitol, glycose, sucrose, and polyethylene glycol, polypropylene glycol, and polybutylene glycol obtained by adding alkylene oxide to these. When the molecular weight of the chain extender exceeds 400, the temperature dependence of the elastic modulus becomes large. The preferred molecular weight ranges from 32 to 200. In the present invention, the preferred blending ratio is about 10 to 40 parts by weight of the polyester polyol (2) and about 25 parts by weight of the chain extender (3) to 100 parts by weight of the polyol component (1).
~50 parts by weight. The polyisocyanate used in the present invention is
It mainly consists of 2,4 and 2,6-tolylene diisocyanate, their isomer mixtures (TDI), and 4,4'-diphenylmethane diisocyanate (MDI), with MDI being particularly preferred. In particular, liquid MDI partially modified by carbodiimide, and polyphenylpolymethylene polyisocyanate (crude) obtained by aniline-formaldehyde condensation and then phosgenation.
MDI) are preferred, and mixtures thereof are also suitable. Furthermore, the polyisocyanate can also be used as a prepolymer with part or all of the above-mentioned or low molecular weight polyols or polyester polyols. In the present invention, the reaction ratio between the polyol component and the isocyanate component may be a ratio commonly used in this type of urethane elastomer, and the isocyanate group/active hydrogen equivalent ratio (i.e., NCO index) may be adjusted to a range of 1.05 to 1.15. It is preferable to react. If the NCO index is lower than 1.05, the mechanical properties of the resulting elastomer will deteriorate, and if it is higher than 1.15, the impact strength will be significantly reduced, and the dimensional stability during mold release will be poor, resulting in
The product then expands, making it difficult to remove the molded product from the mold. In the present invention, in order to obtain a polyurethane elastomer having a low specific gravity, the elastomer may be produced in the presence of a blowing agent if necessary. The blowing agent is preferably a low boiling point organic compound such as monochlorotrifluoromethane or dichloromethane. In order to further improve the mechanical strength of the high modulus urethane elastomer in the present invention, an inorganic reinforcing material can be added. In this case, suitable inorganic reinforcing materials include milled glass fiber, which is made by cutting individual filaments into short pieces to facilitate uniform dispersion in the urethane raw material, or chipped strand glass fiber, which is made by cutting a bundle of filaments into short pieces. . If the surface of these glass fibers is treated with a silane coupling agent, the physical properties will be further improved. Other preferred reinforcing materials include mica, Wollastonite, various mineral fibers, and carbon fibers. The loading amount of these reinforcing materials is preferably about 5 to 30% by weight based on the urethane elastomer produced. As for the wedge-filling method, it may be added to either the polyol component or the polyisocyanate component, but it is generally preferable to use it by blending it into the polyol component. When adding a reinforcing agent, the NCO index is preferably about 1.15 at most, although it depends on the amount added. This is because the isocyanate reacts with the water contained in the reinforcing agent and the active hydrogen on the surface of the reinforcing agent, so it is necessary to increase the NCO index accordingly. When molding a urethane elastomer, there is inevitably moisture in addition to the active hydrogen of the polyol component, and taking this into account, the NCO index for equivalence is empirically in the range of 1.05 to 1.15. Further, for the reaction of the OH component and the NCO component, either the one-shot method or the prepolymer method can be selected, but in the latter case, it is preferable to carry out the reaction by adding part or all of the polyester polyol to the polyisocyanate component. Next, the present invention will be explained in detail based on examples. The distribution materials and test methods used are as follows. (1) Distribution material High molecular weight polymer polyol Polymer polyol POP31-28: Manufactured by Mitsui Nisso Polyurethane Co., Ltd. Average number of functional groups: Approx. 3 Average molecular weight: Approx. 6000 Polyester polyol Orthophthalic acid, 1,6 hexanediol (55wt%), diethylene glycol (21wt%) , consisting of trimethylolpropane (24wt%), with an average functional group number of about 3,
Polyester polyol with average molecular weight of approximately 1150 Orthophthalic acid, glucose (45wt
%), propylene glycol (55wt%), average number of functional groups approximately 5, average molecular weight approximately
650 Polyester Polyol Adipic Acid, Diethylene Glycol (50wt%) Ethylene Glycol (50wt%)
consisting of an average number of functional groups of 2 and an average molecular weight of approx.
1500 comparative polyester polyol Aniline alkylene oxide adduct
KA500: Polyisocyanate manufactured by Mitsui Nisso Urethane Co., Ltd. CL02 Manufactured by Mitsui Nisso Urethane Co., Ltd., liquid modified MDI NCO approximately 29% MTL manufactured by Mitsui Nisso Urethane Co., Ltd., liquid modified MDI NCO approximately 29% (2) Physical property test method Flexural modulus; Conforms to ASTM D790-71 Temperature index: Quotient of flexural modulus at -30℃ and 70℃ (-30℃/70℃) Heat sag (heat sag test) 150mm (length) x 25mm (width) x 3mm ( thickness)
The test piece was left horizontally in a constant temperature bath at 150°C with a 100 mm overhang, and after 1 hour it was taken out and left at room temperature for 30 minutes, after which the amount of sag at the tip was measured. Examples 1 to 4 For each example listed in Table 1, each component was placed in a high-pressure injection molding machine (Krauss Maffei PU80/
Six types of urethane elastomers were obtained by mixing and casting the required amount prepared to have a specific gravity of 1.00 into a 3 mm thick flat plate mold (made of iron) kept at 50±5°C using 40). Various physical property tests were conducted on test pieces cut from the obtained urethane elastomer, and the results are also shown in Table 1. In addition
The NCO index was adjusted to 1.05. Comparative Examples 1 to 3 In place of the polyester polyol in the formulation used in Examples 1 to 6, aniline/alkylene oxide adduct and/or adipic acid polyester polyol was used, and the other results were the same. It is shown in Table 2. Since polyester polyol has poor compatibility with other polyol components, it was mixed with polyisocyanate at 50° C. and dissolved before use.

【table】

[Table] As shown in Table 1, the urethane elastomer reacted using the polyester polyol of the present invention yields a urethane elastomer with a well-balanced property, characterized by heat resistance and high elasticity, which is unprecedented. be able to. In other words, improving the solubility of chain extenders When polymerizing high modulus urethane elastomers, chain extenders are often added in an amount of 20% by weight or more based on the high molecular weight polyol, but in conventional compounding systems, this is difficult to dissolve. There was a strong tendency for the solution to separate, making it difficult to maintain a homogeneous stock solution. Therefore, without using amine-based polyols etc.,
It has been impossible to obtain an elastomer with a high elastic modulus by incorporating a large amount of chain extender. However, when the phthalic acid-based polyester polyol of the present invention is mixed and used, the solubility of the chain extender in the polyol component is improved, so even if a large amount of extender is used, a homogeneous stock solution can be easily maintained. . Improvement of high elastic modulus In the present invention, the synergistic effect of the chain extender and the phthalic acid polyester polyol improves the temperature dependence of heat resistance and elastic modulus, and at the same time,
High elastic modulus can be obtained. As shown in Comparative Examples 3 and 4, adipic acid-based polyester polyols do not exhibit such a synergistic effect and cannot be expected to improve the elastic modulus. With conventional urethane elastomers made from a combination of high molecular weight polyols and chain extenders, it has been difficult to achieve a flexural modulus exceeding 5000 Kg/cm ² . Further, as shown in Comparative Example 1, if an amine polyol is used in combination, a high elastic modulus can be obtained, but on the contrary, the heat resistance becomes extremely poor and the temperature dependence of the elastic modulus also worsens. Improvement of Heat Resistance As mentioned above, the urethane elastomer combined with an amine polyol can have a considerably high flexural modulus, but has poor heat resistance. For example, in Comparative Examples 1 and 2, the heat sag at 150° C. was 43 mm and 64 mm, respectively, resulting in poor heat resistance. When using adipic acid polyester polyol,
For example, in Comparative Examples 3 and 4, the heat sag was large and the heat resistance was not improved. It is clear that the heat resistance of the urethane elastomer of the present invention was improved due to the synergistic effect of the chain extender and the phthalic acid polyester polyol as shown in the examples. Low temperature dependence of elastic modulus The temperature index (-30°C/70°C) of the bending elastic modulus of conventional urethane elastomers is
In the comparative examples, the temperature index exceeded 5 and the influence of temperature change was large, but the elastomer of the present invention had an extremely low temperature index of 3 or less, which is due to the temperature dependence of the elastic modulus. It shows a low level of sexuality. High Productivity According to the present invention, since the green strength (for example, tear strength and ultimate elongation upon demolding) is high, demolding time is fast, and demolding can be performed in 30 to 60 seconds. This is because the phthalic acid polyester polyol has a high cohesive force and the addition of polyester makes it possible to obtain a morphologically uniform polymer. On the other hand, if 30 parts or more of ethylene glycol is added as a chain extender and no polyester polyol is used, the demolding time will be at least 5 parts.
It usually takes 10 times more. Since the present invention has a fast demolding time suitable for RIM, high productivity is possible. Since the urethane elastomer of the present invention has excellent properties as described above, its uses include:
For example, it is extremely suitable for molding automobile fenders, grill opening panels, deck lids, hoods, etc.

Claims (1)

[Scope of Claims] 1 (1) A high molecular weight product obtained by graft polymerization of a vinyl compound mainly composed of styrene acrylonitrile, which has a functional group number of 2.1 to 3 and an average molecular weight of 2000 to 8000. 100 parts by weight of a polymer polyol, (2) having an average molecular weight of 300 to 2000, containing at least 30% by weight of phthalic acid residues and at least 2 hydroxyl groups;
about 10 to 40 parts by weight of a polyester polyol, (3) 25 to 50 parts by weight of a chain extender having a molecular weight of 400 or less, and (4) polyisocyanate, adjusted as necessary so that the NCO index is about 1.05 to 1.15. A method for producing a heat-resistant, high-modulus urethane elastomer having a flexural modulus of 5000 (Kg/cm ² ) or more at room temperature, which comprises reacting in the presence of a foaming agent.