JPS60229924A - Production of impact-resistant polyamide - Google Patents

Abstract

PURPOSE:To obtain an impact-resistant polyamide having a low rate of change even after the influence of high-temperature environment in a low catalyst concentration, by using a specific isocyanate as a polymerization accelerator in anionic polymerization of an omega-lactam. CONSTITUTION:A substantially anhydrous >=5-membered ring omega-lactam is polymerized in the presence of (A) 0.5-2.5mol% anionic polymerization catalyst, e.g. sodium hydride, (B) 1-60pts.wt., based on 100pts.wt. omega-lactam, liquid elastomer having hydroxyl groups at the end or side chain, <=10,000, preferably 1,000- 10,000mol.wt. and 1-3 hydroxyl groups in 1mol and (C) a polymerization accelerator selected from xylene diisocyanate, hydrogenated xylene diisocyanate or hexamethylene diisocyanate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an impact-resistant polyamide, and more particularly, to a method for producing a polyamide that hardly loses its impact resistance even after being exposed to a high-temperature environment 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, a polyamide obtained from ε-caprolactam is known as nylon-6, which has a wide range of uses because of its excellent mechanical and thermal properties. In addition, 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, to improve the impact resistance of nylon-6, it is generally known to copolymerize it with reactive elastomers, for example in British Patents 1067153 and 109926.
No. 5 discloses the use of a reaction product of a polyester polyol and a diisocyanate as a reactive elastomer, and US Pat. No. 3,758,631 discloses the use of a reaction product of a polyester polyol and a diisocyanate as a reactive elastomer. , and furthermore,
B-41958 and German Patent No. 2014505 disclose a method in which polyether glycol and diisocyanate are added simultaneously to the polymerization reaction system.

According to these methods, by changing the amount of elastomer or diisocyanate, its physical properties can be varied in various ways.

However, in order to improve the impact resistance with these methods, and especially to speed up the molding cycle, a high catalyst concentration (3 mo1%) was used.
The results of the present invention have revealed that when the molded product is left at a high temperature of 100° C. or higher for a long period of time and cooled, its 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 during molding, and an impact strength of 10 kgcm/cm or more after heat treatment at 160°C for 0.5 hours. /cm. This trend is
It has become clear that the higher the catalyst concentration, the stronger the effect appears.

In this way, when using conventional methods to increase the impact resistance, but also to shorten the molding cycle by increasing the melting concentration, the resulting molded product has greatly reduced impact resistance due to heat treatment and has extremely unstable physical properties. Due to these drawbacks, they cannot be used for automobile exterior panels, home appliance housings, business machine housings, etc., which require painting at high temperatures of 150 to 250° C., for example.

The present invention improves these drawbacks, allows the reaction to be sufficiently completed within the same reaction time as conventional methods even at low catalyst concentrations, and allows the obtained product to withstand even after being exposed to high temperature environments of 100°C or higher. An object of the present invention is to provide a manufacturing method that reduces the rate of change in impact resistance.

That is, the feature of the present invention is that when a substantially anhydrous 5-membered ring or more ω-lactam is anionically polymerized, the ω-lactam is treated with an anionic polymerization catalyst having a concentration of 0.5 to 2.5 mo1%, a terminal or side chain. A method for producing an impact-resistant polyamide obtained by polymerizing a liquid elastomer having hydroxyl groups in the presence of a polymerization accelerator selected from xylene diisocyanate, hydrogenated xylene diisocyanate, or hexamethylene diisocyanate. be.

In this way, if a specific isocyanate is used, the reaction can be completed within the conventional reaction time even if the concentration of anionic polymerization catalyst is half of the conventional one, and the resulting product can also be produced at high temperatures. Even when left in the environment, the rate of change in impact resistance is extremely small.

Examples of the polymerization accelerator mentioned above include xylene diisocyanate, hydrogenated xylene diisocyanate, hexamethylene diisocyanate, or a combination of multiple of these three, with xylene diisocyanate being the most suitable. be. According to these polymerization accelerators, compared to conventionally used polymerization accelerators such as toluene diisocyanate and polymethylene polyphenyl diisocyanate, the same polymerization can be completed in the same curing time at less than half the catalyst concentration. You can get sex. For example, when using conventional toluene diisocyanate, at least 3 mo1% of the catalyst is required to reduce the curing time to 5 minutes or less, but if xylene diisocyanate is used, 1 mo1% is sufficient to complete the polymerization. can get.

The ω-lactam used in the present invention has a 5- to 12-membered ring, such as α-pyrrolidison, piperidone,
valerolactam, caprolactam, capryllactam,
Among lauryl lactam and the like, 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 inhibit 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, etc., and their hydrides or hydroxides, as well as other anionic polymerization catalysts, For example, it may be a Grignard reagent.

Considering its economy, safety, and reactivity, alkali metal hydrides, such as sodium hydride, are suitable.

Its blending amount is approximately 0.5 to 2.5 to ω-lactam.
m01% is appropriate. As mentioned above, if the amount of the catalyst is too small, the degree of reaction completion will be poor, and if the amount is too large, the impact resistance will tend to decrease.

Further, the liquid elastomer having a hydroxyl group at the terminal or side chain used in the present invention must be soluble in the molten ω-lactam.

For example, polyether polyols, polybutadiene polyols, polynitrile-butadiene polyols, polyisoprene polyols, etc. are suitable. However, polyester polyols and polychloroprene polyols are unsuitable, and it is difficult to achieve the object of the present invention. Its molecular weight is
10,000 or less, preferably 1,000 to 10,00
Furthermore, the optimal amount of hydroxyl groups contained in the elastomer is 1 to 3 per molecule; anything larger than this will have an adverse effect, such as inhibiting the polymerization reaction or 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.

Further, the amount thereof to be blended is suitably 1 to 60 parts by weight, preferably 15 to 40 parts by weight, per 100 parts by weight of ω-lactam.

In addition, in order to obtain even 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, and these Surface treatment of the filling agent 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, but first, a polymerization accelerator such as xylene diiso-4 cyanate is reacted with a liquid elastomer having a hydroxyl group at the terminal or side chain. A method of adding the product to an ω-lactam liquid containing an anionic polymerization catalyst, or a method of adding the above liquid elastomer to an ω-lactam liquid and adding a polymerization promoter such as xylene diisocyanate and an anionic polymerization catalyst to another ω-lactam liquid. There is a method of mixing the respective added ω-lactam solutions. According to this method, 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 0.5 to 6 mo 1%.
, xylene diisocyanate and other polymerization accelerators are set in a range of 1 to 3.0 mo1%.

Next, specific embodiments of the method of the present invention will be explained by showing Examples, but it goes without saying that the present invention is not limited to these Examples.

Example 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 beaker. Both beakers were heated and dehydrated at 110° C. and 2 mmHg for 140 hours, and then replaced with nitrogen to maintain the liquid temperature at around 100° C. A predetermined amount of xylene diisocyanate (XDI) was added to the system to which the hydroxyl-terminated polybutadiene was added, and a predetermined amount of 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 a physical property test was conducted. The result - the second
Shown in the table.

Margin Table 1: Bimon hydroxyl group-terminated polybutadiene;
3 TDI; 2.4/2.6≧8/2 Sodium hydride; Mixture content of sodium hydride and oil 63
% Table 2 *I ASTM2! I will definitely follow. However, the sample thickness is 2.5n■
.

*2 1 g of sample was quenched in warm water at (a) ℃ for 8 hours.
Weight change rate before and after extraction*3 Weight change rate before and after chloroform extraction*4 Orb A internal stabilization at 160°C for 0.5 hours*5 Xylene diisocyanate was used as a polymerization accelerator in Example 1 without l#i When the catalyst (sodium hydride) was adjusted to 1 mo1%, the impact strength of the resulting product did not change much even after heat treatment, and there was little unreacted material (ε-caprolactam oligomer or unreacted elastomer). .

In Example 2, when xylene diisocyanate was used as a polymerization accelerator and the catalyst amount was 2 mo1%, the resulting product had a lower hot water extraction rate than the product of Example 1. In other words, this indicates that there is a small amount of water-soluble unreacted substances or reactants (epsilon-caprolactam or epsilon-caprolactam oligomer). On the other hand, the solvent extraction rate is increasing. This indicates that chloroform-soluble unreacted substances or reactants (unreacted substances or oligomers of the reactive elastomer) are increasing.

Putting these two results together, if the amount of catalyst increases,
This shows that the polymerization of ε-caprolactam is promoted, but on the other hand, the urethane bond that is the bond between the elastomer and poly ε-caprolactam is broken.

In Comparative Example 1, when tolylene diisocyanate was used as a polymerization accelerator and the catalyst amount was 1 mo1%, the obtained product was very soft and had excellent impact strength. Moreover, 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 believed that unreacted substances act as plasticizers in the product and improve 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 2, when tolylene diisocyanate was used as a polymerization accelerator and the catalyst amount was 3 mo1%, 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 above, these phenomena are thought to be due to the excessive amount of catalyst promoting the cleavage of urethane bonds.

Further, in Example 3, when hexamethylene diisocyanate was used as a polymerization accelerator and the catalyst amount was 1 mo1%, the resulting product had excellent impact strength, but this property was impaired by heat treatment. However, it can be seen that the hot water extraction rate and solvent extraction rate are closer to Example 1 than Comparative Example 1. Although xylene diisocyanate is optimally used to achieve the objectives of the present invention, hexamethylene diisocyanate is believed to be more suitable than tolylene diisocyanate.

As described above, the degree to which the purpose of the present invention is achieved differs depending on the type of polymerization accelerator. According to research accompanying the present invention, xylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, methylene diphenyl diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate, in the order of is easy to achieve. Using xylene diisocyanate 1
In this case, high-speed curing is possible with the minimum amount of catalyst, and it is possible to obtain a product with stable properties within the shortest possible time. In addition to this, hydrogenated xylene diisocyanate and hexamethylene diisocyanate may also satisfactorily achieve the object of the present invention.

Patent applicant: Sanso Star Belt Co., Ltd.

Claims (1)

[Claims] 1. In anionically polymerizing a substantially anhydrous ω-lactam having a 5-membered ring or more, the ω-lactam is 0.5 to 2.5
an anionic polymerization catalyst having a concentration of 11101%, a liquid elastomer having a hydroxyl group at the terminal or side chain, and a polymerization accelerator selected from xylene diisocyanate, hydrogenated xylene diisocyanate, or hexamethylene diisocyanate. A method for producing impact-resistant polyamide, characterized by polymerizing it in the presence of a polyamide.