JPH0412292B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing impact-resistant polyamide,
Specifically, it relates to a method for producing polyamide that hardly loses its impact resistance even after being exposed to high-temperature environments of 100°C or higher. It has been known for a long time that ω-lactams are generally polymerized at temperatures above their melting point in the presence of an anionic polymerization catalyst, and addition of compounds containing isocyanates allows for faster polymerization at lower temperatures. It is also well known to do so. Polyamides obtained in this way are currently used for various purposes. For example, polyamide that can be obtained from ε-caprolactam is
Known as nylon-6, it has a wide range of uses due to its excellent mechanical and thermal properties. Also,
Polyamide that can be obtained from lauryl lactam is known as nylon-12 and has excellent water absorption and impact resistance, which are disadvantages of nylon-6. Furthermore, in order to improve the impact resistance of nylon-6, it is generally known to copolymerize it with a reactive elastomer. It has been disclosed that the reaction product of
No. 3758631 describes the use of a reaction product of polyester polyol and diisocyanate as a reactive elastomer, and Japanese Patent Publication No. 48-41958 and German Patent No. 2014505 disclose the use of polyether glycol and diisocyanate in a polymerization reaction system. A method of simultaneous addition is shown. According to these methods, by varying the amount of elastomer or diisocyanate,
Its physical properties can be changed in various ways. However, when using these methods to improve impact resistance and using a high catalyst concentration (e.g. 3 mol%) to speed up the molding cycle, the resulting molded products
If you leave it at a high temperature of 100℃ or more for a long time and cool it,
The results of the present invention have revealed that the impact resistance is significantly reduced. For example, a molded product obtained by the method according to German Patent No. 2014505 has an impact strength of 100 Kgcm/cm or more in the notched Izot impact test according to ASTM D256, and 10 Kgcm/cm after heat treatment at 160°C for 0.5 hours.
cm/cm. It has become clear that such a tendency appears more strongly as the catalyst concentration increases. In this way, when conventional methods use a high catalyst concentration to shorten the molding cycle, as well as to increase the impact resistance, the resulting molded product has greatly reduced impact resistance due to heat treatment and has extremely unstable physical properties. Due to this drawback, it cannot be used for automobile exterior panels, housings for home appliances, housings for business machines, etc., which require painting at high temperatures of 150 to 250°C. The present invention improves these drawbacks, allows the reaction to be fully completed within the same reaction time as conventional methods even at low catalyst concentrations, and provides the resulting product with impact resistance even after being exposed to high temperatures of 100°C or higher. The purpose of the present invention is to provide a manufacturing method that reduces the rate of change in sex. That is, the feature of the present invention is that when a substantially anhydrous 5-membered ring or more ε-lactam is anionically polymerized, an anionic polymerization catalyst having a concentration of 0.5 to 2.5 mol% with respect to the ω-lactam is added to the terminal or side chain. A method for producing an impact-resistant polyamide obtained by polymerizing a liquid elastomer having a hydroxyl group and xylene diisocyanate. If xylene diisocyanate is used as a polymerization accelerator in this way, the reaction can be completed within the conventional reaction time even with half the concentration of anionic polymerization catalyst as in conventional methods, and the resulting product Even after being left in a high-temperature environment, the rate of change in impact resistance is extremely small. If the above-mentioned xylene diisocyanate is used, compared to conventionally used polymerization accelerators such as toluene diisocyanate and polymethylene polyphenyl diisocyanate, it is possible to achieve the same results with less than half the catalyst concentration and within the same curing time. Polymerization completion can be obtained. for example,
Conventionally, when using toluene diisocyanate, at least 3 mol was required to reduce the cure time to 5 minutes or less.
% of catalyst is required, but if xylene diisocyanate is used, sufficient polymerization can be completed with 1 mol%. The ω-lactam used in the present invention has a 5- to 12-membered ring, such as α-pyrrolidinone,
piperidone, valerolactam, caprolactam,
Among capryllactam, lauryllactam, etc., ε-caprolactam is particularly suitable for the present invention. Furthermore, there is no problem with lactams having any substituents on the carbon chain as long as they do not interfere with the polymerization reaction. Furthermore, these omega-lactams must be substantially anhydrous in the practice of this invention. This is because water becomes a polymerization catalyst poison. In addition, the anionic polymerization catalyst used in the present invention includes alkali metals, alkaline earth metals such as sodium, potassium, magnesium, and their hydrides or hydroxides, and other anionic polymerization catalysts such as It may also be a Grignard reagent. Considering its economy, safety, and reactivity, alkali metal hydrides, such as sodium hydride, are suitable. The blending amount is about 0.5 to ω-lactam.
2.5 mol% is appropriate. If the amount of catalyst is too small,
As mentioned above, the degree of reaction completion is still poor, and if too much is used, the impact resistance tends to decrease when left in a high temperature environment. In addition, the liquid elastomer having a hydroxyl group at the terminal or side chain used in the present invention is
Must be soluble in the lactam. For example, polyether polyols, polybutadiene polyols, polyacrylonitrile-butadiene polyols, polyisoprene polyols, etc. are suitable. However, polyester polyol,
Polychloroprene polyols are unsuitable and difficult to achieve the objectives of the invention. The molecular weight of the liquid elastomer is 10,000 or less, preferably 1,000 to 10,000,
Further, the optimal amount of hydroxyl groups contained in the elastomer is 1 to 3 per molecule; anything more than this may inhibit the polymerization reaction or have adverse effects such as reducing the molecular weight of the product. Furthermore, these elastomers need to be added to the polymerization system in anhydrous form for the reasons mentioned above. In addition, the appropriate amount is 1 to 60 parts by weight, preferably 15 parts by weight, per 100 parts by weight of ω-lactam.
~40 parts by weight. In addition, in order to obtain better mechanical properties or better dimensional stability in the method of the present invention, it is also possible to disperse glass fibers, calcium carbonate, etc. into the polymer for reinforcement. Surface treatment of fillers is useful from the viewpoint of workability and physical properties. In the method of the present invention, various methods are possible for adding each component to the ω-lactam polymerization system. A method in which the product is mixed with an ω-lactam liquid and then added to another ω-lactam liquid containing an anionic polymerization catalyst, or an ω-lactam liquid containing the above liquid elastomer and a polymerization accelerator, xylene diisocyanate and an anion. There is a method of mixing with another ω-lactam liquid to which a polymerization catalyst has been added. At that time, the reaction between the liquid elastomer and xylene diisocyanate is carried out using a compounding amount in which the NCO group of the xylene diisocyanate is equal to or more than the equivalent of the OH group of the liquid elastomer, preferably about 1.5 to 10 equivalents, This is carried out by stirring for 5 to 60 minutes under normal pressure at a temperature ranging from room temperature to about 100°C. When mixing this reaction product and the ω-lactam liquid, for example, first mix the lactam liquid with approx.
After dehydrating at 100℃, store at room temperature or approx.
It is carried out by adding the reaction product which has been heated to a temperature below 100°C. The mixture of the reaction product and ω-lactam liquid thus obtained is maintained at a temperature of, for example, about 70 to 150°C,
A separately prepared mixture of anionic polymerization catalyst and ω-lactam liquid is also kept at about 70 to 150°C,
Both liquids are used for reaction injection molding.
Molding (abbreviated as RIM)) By simultaneously injecting both liquids into a mold at high pressure and high speed, both liquids react and harden and are molded at the same time. According to these methods, when polyamide is polymerized by the RIM method, the reaction can be completed within 3 minutes. Of course, in this case, the concentration of the anionic polymerization catalyst is between 0.5 and ω-lactam.
The range is set to 2.5 mol%. The concentration of xylene diisocyanate is between 1 and ω-lactam.
It is preferably set within a range of 3.0 mol%. Next, specific aspects and effects of the method of the present invention will be explained by showing examples and comparative examples.
It goes without saying that the present invention is not limited to these examples. Examples and Comparative Examples Various polyamides were obtained according to the ingredient list shown in Table 1. In the polymerization method, first, a predetermined amount of ε-caprolactam is equally divided into two beakers, and a predetermined amount of hydroxyl-terminated polybutadiene is further placed in one of the beakers. Then heat both beakers to 110℃.
The solution was dehydrated by heating at 2 mmHg for 1.0 hour, and then replaced with nitrogen to maintain the liquid temperature at around 100°C. A predetermined amount of polymerization accelerators (xylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), methylene diphenyl diisocyanate ( MDI) or polyphenylpolymethylene diisocyanate), and a predetermined amount of polymerization catalyst (sodium hydride) was added to the other system. After being left for 15 minutes, the liquids in both beakers were stirred and mixed, poured into a mold preheated to 150°C, and left to stand for 3 minutes, then the molded product was taken out and cooled to room temperature. Thereafter, the sample was stored in a desiccator dried with silica gel, and then physical property tests were conducted. The results are shown in Table 2.

【table】

【table】

[Table] In Example 1, xylene diisocyanate was used as a polymerization accelerator and the catalyst (sodium hydride)
When the amount was 1 mol %, the impact strength of the obtained product did not change much even after heat treatment, and the amount of unreacted substances (ε-caprolactam oligomer or unreacted elastomer) was small. In Example 2 and Example 3, xylene diisocyanate was used as a polymerization accelerator, and the amount of catalyst was
When the concentrations were 2 mol % and 3 mol %, the resulting product had a lower hot water extraction rate than the product of Example 1. In other words, water-soluble unreacted substances or reactants (ε
-caprolactam or ε-caprolactam oligomer). On the other hand,
Solvent extraction rates are increasing. This indicates that chloroform-soluble unreacted substances or reactants (unreacted substances or oligomers of the reactive elastomer) are increasing. To summarize these results, increasing the amount of catalyst promotes the polymerization of ε-caprolactam, but
On the other hand, it shows that the urethane bond, which is the bond between the elastomer and polyε-caprolactam, has been broken. In Comparative Example 4, when tolylene diisocyanate was used as a polymerization accelerator and the catalyst amount was 1 mol %, the obtained product was very soft and had excellent impact strength. In addition, its impact strength is not impaired even by heat treatment. On the other hand, both the hot water extraction rate and the solvent extraction rate showed abnormally large values, indicating that the reaction was not progressing sufficiently. Therefore, it is thought that the unreacted substances act as plasticizers in the product and improve the impact strength. Moreover, if such a product is left in the atmosphere, unreacted substances will precipitate on the surface, making it unusable as an industrial material. In Comparative Example 5, when tolylene diisocyanate was used as a polymerization accelerator and the catalyst amount was 3 mol%, the resulting product had excellent impact strength, but on the other hand, its properties were significantly impaired by heat treatment. . Moreover, the hot water extraction rate is much higher than that in Example 1. As mentioned earlier, these phenomena
This is considered to be because the amount of catalyst was too large, which promoted the cleavage of urethane bonds. In addition, in Comparative Example 1, hexamethylene diisocyanate was used as a polymerization accelerator, and the catalyst amount was 1
When the concentration is ~3 mol %, the resulting product has excellent impact strength, but the hot water extraction rate and solvent extraction rate are slightly inferior to those using xylene diisocyanate. To achieve the objectives of the present invention, xylene diisocyanate is optimally used. As described above, when xylene diisocyanate is used, high-speed curing is possible with a minimum amount of catalyst, and it has become possible to obtain a product with stable properties within the shortest possible time. In Comparative Examples 6 and 7 and Comparative Examples 8 and 9, the same tendency as in Comparative Examples 4 and 5 described above is observed. That is, when the catalyst amount is 1 mol %, the impact strength is not impaired even by heat treatment, but both the hot water extraction rate and the solvent extraction rate show large values. On the other hand, when the catalyst amount is 3 mol %, the impact strength is significantly impaired by heat treatment. It is therefore clear that the objects of the invention are not achieved by methylene diphenyl diisocyanate or polyphenyl polymethylene diisocyanate.

Claims (1)

[Claims] 1. In anionically polymerizing a substantially anhydrous 5-membered or more ω-lactam, an anionic polymerization catalyst having a concentration of 0.5 to 2.5 mol% relative to the ω-lactam;
A method for producing an impact-resistant polyamide, comprising polymerizing the above ω-lactam in the presence of a liquid elastomer having a hydroxyl group at the terminal or side chain and xylene diisocyanate.