JP6805030B2 - Monomer casting composition and polyamide molded product and its manufacturing method - Google Patents

Description

The present invention relates to a composition for forming a polyamide molded product by a monomer casting method, a polyamide molded product formed from this composition, and a method for producing the same.

Among the molding methods for polyamide moldings, the monomer casting method (monomer casting method or monomer casting method), which utilizes the property that anhydrous lactam rapidly polymerizes by anionic polymerization, is a large and thick molded body (resin material). Is a molding method obtained in one step. The shape of the obtained polyamide molded product is usually plate-shaped or rod-shaped, and in general, the plate-shaped or rod-shaped molded product is further machined into a predetermined shape to manufacture mechanical parts or the like. However, in the monomer casting method, since a large molded product is produced by rapid polymerization, a locally non-uniform polymerization reaction occurs and the temperature gradient between the surface and the inside is large, so that the crystallization is non-uniform. As it progresses, inhomogeneous flow patterns due to local fine spherulites and crack-like internal defects are likely to occur.

Therefore, Japanese Patent Application Laid-Open No. 58-17914 (Patent Document 1) states that, as a method for producing a polyamide molded product having no internal defects, substantially anhydrous ω-lactam is equal to or higher than the melting point of ω-lactam, and the produced polyamide is produced. When polymerizing in the presence of an anionic polymerization catalyst and a polymerization co-catalyst at a temperature equal to or lower than the melting point of ω-lactam, polyamide particles having a particle diameter of about 400 μm or less and a melting point of 200 ° C. or higher were made into 0. A method of adding 01 to 1 part by mass is disclosed. Further, it is generally known that inorganic particles such as cobalt blue and talc and alkali metal salts of higher fatty acids function as a nucleating agent for polyamide, but in the method of Patent Document 1, polyamide particles are used as a nucleating agent. Is added to produce a molded product having a uniform size and a large number of spherulites being formed to produce a molded product having no crack-like internal defects or internal flow patterns. In particular, the method of adding polyamide particles as a nucleating agent has a high nucleating effect, and not only a molded body having no crack-like internal defects or internal flow patterns can be obtained, but also a molded body having high hardness and elastic modulus. Can also be obtained.

In the case of a crystalline resin, the toughness is generally improved by refining the spherulite, but it can be obtained by a method of refining the spherulite using a nucleating agent as in Patent Document 1. As the spherulite becomes finer, the crystallinity of the obtained polyamide molded product increases, and the rigidity increases, but the toughness does not improve or rather decreases, so that cracks and chips are likely to occur during processing and use. ..

On the other hand, a method of reducing internal defects in the molded product by pressure molding has also been proposed. However, even in pressure molding, as the polymerization progresses, the viscosity of the raw material containing the polymer increases and the effect of pressurization decreases, so that the characteristics of the molded product cannot be sufficiently improved.

Therefore, in Japanese Patent Application Laid-Open No. 2006-143999 (Patent Document 2), a polymerizable lactam solution obtained by adding at least an anionic polymerization catalyst and an anionic polymerization initiator to substantially anhydrous lactam is cast into a mold and pressurized. In a method for producing a polyamide resin molded product in which a member is inserted into an opening and polymerized by pressurizing and heating, a method for producing a polyamide resin molded product in which an external lubricant is mixed with polymerizable lactam is disclosed. In this method, the adhesiveness between the resin and the surface of the molding machine is improved by the action of an external lubricant having a function of improving the slippage between the polymer and the metal to prevent adhesion and improving the peelability of the molded product from the mold surface. We are manufacturing a molded product that has no internal defects. In this document, ethylene oxide adducts of higher alcohols, ethylene oxide adducts of bisphenol, polyethylene glycols, waxes (microcrystalin wax, polyolefin wax, etc.), and triallyl isocyanurates are described as external lubricants. An ethylene oxide adduct of bisphenol, triallyl isocyanurate, is used.

However, this method requires a device for pressurizing, and the manufacturing process is complicated.

On the other hand, Japanese Patent Application Laid-Open No. 2002-302547 (Patent Document 3) states that in order to improve the elastic recovery of the polyamide molded product, polyethylene glycol 4 to 96 to 84 mol% of cyclic amide and a number average molecular weight of 200 to 600 are used. A method for producing a polyamide elastomer molded product by reacting with 16 mol% is disclosed.

However, in this document, an elastomer in which polyethylene glycol is introduced into the molecule is synthesized, and there is no description about improvement of internal defects of a hard and highly rigid polyamide molded product.

JP-A-58-17914 (Claims) JP-A-2006-143999 (Claim 1, Effect of Invention, Paragraphs [0029] [0030], Examples) JP-A-2002-302547 (Claim 1, Example)

Therefore, an object of the present invention is to provide a monomer casting composition capable of suppressing cracking and chipping of a polyamide molded product during processing and use, a polyamide molded product formed of this composition, and a method for producing the same. is there.

Another object of the present invention is to provide a method for easily producing a polyamide molded product having high toughness while maintaining rigidity (high hardness and elastic modulus) by a monomer casting method.

As a result of diligent studies to achieve the above problems, the present inventor has made a combination of lactam, a nucleating agent containing polyamide particles having a melting point equal to or higher than the polymerization temperature of lactam, and a toughness-imparting agent containing polyalkylene glycol. The present invention has been completed by finding that cracking and chipping of the polyamide molded product during processing and use can be suppressed.

That is, the monomer casting composition of the present invention is a monomer casting composition containing lactam, a nucleating agent and a toughness-imparting agent, and the nucleating agent has a melting point equal to or higher than the polymerization temperature of the lactam. It contains polyamide particles and the toughness-imparting agent contains polyalkylene glycol. The polyalkylene glycol may be polyethylene glycol. The number average molecular weight of the polyalkylene glycol may be about 400 to 50,000. The average particle size of the polyamide particles may be about 1 to 100 μm. The ratio of the toughness-imparting agent is about 0.1 to 5 parts by mass with respect to 100 parts by mass of lactam. The ratio of the toughness-imparting agent is about 50 to 5000 parts by mass with respect to 100 parts by mass of the nucleating agent. The ratio of the nucleating agent is about 0.001 to 1 part by mass with respect to 100 parts by mass of lactam. The lactam may be an anhydrous 5- to 20-membered ring lactam. The composition of the present invention may further contain an anionic polymerization catalyst and an anionic polymerization initiator.

The present invention also includes a method of producing a polyamide molded product by casting a monomer of the composition. Further, in the present invention, a molded product obtained by this method, that is, a polyamide molded product containing a ring-opening polymer of lactam, a nucleating agent and a toughness-imparting agent, wherein the nucleating agent is a polymerization of the lactam. A molded product containing polyamide particles having a melting point equal to or higher than the temperature and containing polyalkylene glycol as a toughness-imparting agent is also included.

In the present invention, since lactam, a nucleating agent containing polyamide particles having a melting point equal to or higher than the polymerization temperature of lactam, and a toughness-imparting agent containing polyalkylene glycol are combined, polyamide molding having high tensile elongation and impact strength is performed. The body can be manufactured, and cracking and chipping of the polyamide molded product during processing and use can be suppressed. Further, by the monomer casting method, it is possible to easily produce a polyamide molded product having high toughness while maintaining rigidity (high hardness and elastic modulus).

FIG. 1 is a polarizing micrograph showing the crystal state of the polyamide molded product obtained in Example 1. FIG. 2 is a polarizing micrograph showing the crystal state of the polyamide molded product obtained in Comparative Example 1. FIG. 3 is a polarizing micrograph showing the crystal state of the polyamide molded product obtained in Comparative Example 2. FIG. 4 is a polarizing micrograph showing the crystal state of the polyamide molded product obtained in Comparative Example 3.

[Polymer casting composition]
The monomer casting composition (polymerizable lactam solution) of the present invention contains lactam, a nucleating agent and a toughness-imparting agent. In the present invention, a polyamide molded product is obtained by casting this composition into a mold, heating and polymerizing.

(Lactam)
As the lactam, ω-lactam having a 5-membered ring or more is usually used. Examples of the ω-lactam include α-pyrrolidone (γ-butyrolactam), α-piperidone (δ-valerolactam), α-caprolactam, ε-caprolactam, ω-enantractam, ω-caprilactam, ω-decanolactam, and the like. Examples thereof include 5 to 20-membered ring lactams such as ω-undecane lactam and ω-laurolactam. These ω-lactams can be used alone or in combination of two or more. Of these ω-lactams, 5 to 13-membered ring lactams such as ε-caprolactam and ω-laurolactam (particularly 6 to 8 membered ring lactams) are preferable.

As the lactam, substantially anhydrous lactam is usually used from the viewpoint of polymerizable property and the like. The water content in lactam may be, for example, 0.01% by mass or less (about 0.001 to 0.003% by mass). In addition, in this specification and claims, "anhydrous lactam" generally means lactam dehydrated under reduced pressure (substantially anhydrous lactam) as a lactam used for monomer casting, and is polymerized. As long as it does not inhibit the above, it may contain water.

(Nucleating agent)
By including a nucleating agent in addition to the lactam, the composition of the present invention can improve the crystallinity of the polyamide molded product obtained by the monomer casting method, and in particular, the polyamide particles (nylon particles or nylon particles or) can be used as the nucleating agent. Since it contains (polyamide powder), uniform spherulites can be generated and internal defects of the molded product can be suppressed.

Since the polyamide particles become the core in the crystallization of the lactam polymer, it is necessary to maintain the particle shape without melting at the polymerization temperature of the lactam. Therefore, the polyamide particles have a melting point equal to or higher than the polymerization temperature of the lactam. Specifically, when the polymerization temperature is T ° C., the melting point of the polyamide particles is, for example, T ° C. to (T + 100) ° C., preferably (T + 10) ° C. to (T + 80) ° C., and more preferably (T + 30) ° C. to It is about (T + 70) ° C. If the melting point of the polyamide particles is lower than the polymerization temperature, the polyamide particles may melt and have no crystal structure before the composition starts crystallization, and the effect as a nucleating agent may not be exhibited.

The polyamide forming the polyamide particles is not particularly limited as long as it has a melting point equal to or higher than the polymerization temperature of the lactam, and a conventional polyamide can be used, and an aliphatic polyamide or an aromatic polyamide may be used. , The aliphatic polyamide is preferable from the viewpoint of excellent affinity with the polyamide obtained by polymerizing the lactam.

Examples of the aliphatic polyamide include polyamide 6, polyamide 11, polyamide 12, polyamide 46, polyamide 66, polyamide 610, polyamide 611, polyamide 612, polyamide 613, polyamide 1010, polyamide 1012, polyamide 66/11, and polyamide 66/12. , Polyamide 6/12/612 and the like. These aliphatic polyamides can be used alone or in combination of two or more. Among these aliphatic polyamides, a polyamide having an alkylene unit (skeleton) common to the polyamide obtained by polymerizing the lactam is preferable. For example, when the lactam is ε-caprolactam, the polyamide 6 or the polyamide 66 or the polyamide 610 is preferable. It may be a polyamide containing a C _4-8 alkylene skeleton such as (especially a polyamide containing a C _5-7 alkylene skeleton such as polyamide 6 or polyamide 66).

The shape of the polyamide particles is not particularly limited, and is, for example, spherical (true spherical or substantially spherical), ellipsoidal (elliptical sphere), polygonal (polygonal pyramid, rectangular parallelepiped, rectangular parallelepiped, etc.), Plate-shaped (flat, scaly, flaky, etc.), rod-shaped or rod-shaped, fibrous, dendritic, amorphous, etc. may be mentioned. The shape of the polyamide particles is usually spherical, ellipsoidal, polygonal, indefinite, or the like. Of these shapes, a substantially spherical shape is preferable from the viewpoint that uniform spherulites can be easily generated.

The average particle size (number average primary particle size) of the polyamide particles is, for example, 1 to 100 μm, preferably 3 to 80 μm (for example, 5 to 50 μm), and more preferably 3 to 30 μm (particularly 15 to 25 μm). The maximum particle size of the polyamide particles may be, for example, 500 μm or less, preferably 300 μm or less, and more preferably 100 μm or less. The minimum particle size of the polyamide particles may be, for example, 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more. If the particle size of the polyamide particles is too small, the polyamide particles tend to aggregate, and it may be difficult to disperse them uniformly in the polymerizable lactam solution. On the other hand, if the polyamide particles are too large, the surface area of the polyamide particles becomes small, and the effect as a nucleating agent may not be exhibited. In the present specification and claims, these particle sizes can be measured by, for example, a method of measuring the dimensions based on a scanning electron micrograph taken at 200 times.

The nucleating agent may contain other nucleating agents in addition to the polyamide particles as long as the effects of the present invention are not impaired. Other nucleating agents include conventional nucleating agents used as polyamide nucleating agents, such as inorganic nucleating agents (eg, mica, kaolin, talc, clay, montmorillonite, cobalt blue, boron nitride, oxidation). Higher grades such as magnesium, aluminum oxide, calcium carbonate, barium sulfate, calcium titanate, organic nucleating agents (eg, lithium stearate, sodium stearate, magnesium stearate, calcium stearate, zinc stearate, aluminum stearate, etc.) Examples thereof include fatty acid metal salts and aryl (sub) phosphate metal salts such as sodium phenylphosphinate). These other nucleating agents can be used alone or in combination of two or more. The shape and particle size of the other nucleating agent can be selected from the same type and range as the polyamide particles, and the preferred embodiment is also the same.

The proportion of the polyamide particles in the nucleating agent may be 50% by mass or more (for example, 50 to 100% by mass), for example, 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more. It may be 100% by mass (polyamide particle alone). If the proportion of polyamide particles is too small, internal defects may occur in the molded product.

The ratio of the nucleating agent (particularly polyamide particles) is, for example, 0.001 to 1 part by mass, preferably 0.005 to 0.8 parts by mass, and more preferably 0.01 to 0 parts by mass with respect to 100 parts by mass of lactam. It is about 5 parts by mass (particularly 0.01 to 0.3 parts by mass). Further, since the balance of various properties such as rigidity is excellent and the toughness such as tensile elongation can be greatly improved, the ratio of the nucleating agent (particularly polyamide particles) is, for example, 0.05 to 100 parts by mass of lactam. It may be about 0.3 parts by mass (particularly 0.06 to 0.2 parts by mass). If the proportion of the nucleating agent is too small, the effect as the nucleating agent is not exhibited, the rigidity of the molded body may be lowered, or internal defects may occur in the molded body. On the other hand, if the proportion of the nucleating agent is too large, the nucleating effect is saturated and there is a possibility that aggregation or precipitation may occur in the polymerizable lactam solution.

(Toughness imparting agent)
In the composition of the present invention, the toughness can be improved while maintaining the rigidity of the polyamide molded product by combining the nucleating agent and the toughness-imparting agent containing polyalkylene glycol.

Examples of the polyalkylene glycol include homopolymers such as _{polyC 2-4} alkylene glycol such as polyethylene glycol (or polyethylene oxide), polypropylene glycol, and polybutylene glycol (polytetramethylene ether glycol), and polyoxyethylene-. Examples thereof include copolymers such as polyoxypropylene copolymers (polyoxyethylene-polyoxypropylene block copolymers, etc.). These polyalkylene glycols can be used alone or in combination of two or more.

Among these polyalkylene glycols, poly C _2-4 alkylene glycols such as polyethylene glycol and polyoxyethylene-polyoxypropylene copolymer are preferable, and polyethylene glycol (or poly) is preferable because the toughness of the molded product can be highly improved. Ethylene oxide) is particularly preferred. In addition, polyethylene glycol and polyethylene oxide are substances having the same chemical structure (basic unit), and generally, when the average molecular weight is about 20,000 or less, it is called polyethylene glycol, and when it exceeds 20,000, it is called polyethylene oxide. However, in the present specification and claims, both are used interchangeably.

The number average molecular weight of polyalkylene glycol (particularly polyethylene glycol) is, in gel permeation chromatography (GPC), in terms of polystyrene, for example, 400 to 50,000, preferably 1000 to 40,000 (for example, 5000 to 35000), and more preferably 1000 to 30000. (Especially about 1500 to 25000). If the molecular weight of the polyalkylene glycol is too low, the polymerization reaction of lactam may be hindered due to the influence of the terminal hydroxyl group, and if it is too large, it becomes difficult to dissolve in the polymerizable lactam solution and the viscosity of the solution increases. , There is a risk that it will be difficult for the mixed air bubbles to escape.

The toughness-imparting agent may contain other toughness-imparting agents in addition to the polyalkylene glycol (particularly polyethylene glycol) as long as the effects of the present invention are not impaired. Other toughness-imparting agents include conventional toughness-imparting agents, such as rubber components (eg, polybutadiene rubber, polyisoprene rubber, polychloroprene rubber, butadiene / isoprene copolymer, butadiene / styrene copolymer, acrylonitrile / butadiene rubber). , Acrylonitrile, butadiene, styrene rubber, etc.), Thermoplastic elastomers (eg, styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyvinyl chloride-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, thermoplastics Polyurethane, etc.). These other toughness-imparting agents can be used alone or in combination of two or more.

The proportion of polyalkylene glycol (particularly polyethylene glycol) in the toughness-imparting agent may be 50% by mass or more (for example, 50 to 100% by mass), for example, 80% by mass or more, preferably 90% by mass or more, more preferably 90% by mass or more. It may be 95% by mass or more, or 100% by mass (polyalkylene glycol alone). If the proportion of polyalkylene glycol is too small, the toughness of the molded product may decrease.

The ratio of the toughness-imparting agent (particularly polyethylene glycol) is, for example, 0.1 to 5 parts by mass, preferably 0.2 to 3 parts by mass, and more preferably 0.3 to 2 parts by mass with respect to 100 parts by mass of lactam. In particular, it is about 0.5 to 2 parts by mass). Furthermore, the ratio of the toughness-imparting agent (particularly polyethylene glycol) is, for example, 0.5 to 100 parts by mass of lactam, because it has an excellent balance of various properties such as rigidity and can greatly improve toughness such as tensile elongation. It may be about 1.5 parts by mass (particularly 0.8 to 1.2 parts by mass). If the proportion of the toughness-imparting agent is too small, the toughness of the molded product may decrease. On the other hand, if the proportion of the toughness-imparting agent is too large, the rigidity of the molded product may decrease.

The ratio of the toughness-imparting agent can be selected from the range of about 10 to 15000 parts by mass with respect to 100 parts by mass of the nucleating agent, for example, 30 to 10000 parts by mass (for example, 50 to 5000 parts by mass), preferably 100 to 4000 parts by mass. (For example, 200 to 3000 parts by mass), more preferably 300 to 2000 parts by mass (particularly 500 to 2000 parts by mass). Furthermore, the ratio of the toughness-imparting agent (particularly polyethylene glycol) is, for example, 500 to 100 parts by mass of the nucleating agent, because the balance of various properties such as rigidity is excellent and the toughness such as tensile elongation can be greatly improved. It may be about 1500 parts by mass (particularly 800 to 1200 parts by mass). If the proportion of the toughness-imparting agent is too small, the toughness may decrease. On the other hand, if the proportion of the toughness-imparting agent is too large, the rigidity of the molded product may decrease or internal defects may occur in the molded product.

(Anionic polymerization catalyst and anionic polymerization initiator)
The composition of the present invention usually contains an anionic polymerization catalyst and an anionic polymerization initiator in addition to the lactam, nucleating agent and toughness-imparting agent.

The anion polymerization catalyst is not particularly limited as long as it is a conventional catalyst used in anion polymerization of ω-lactam, and for example, alkali metals (lithium, sodium, potassium, etc.) and / or alkaline earth metals (magnesium, calcium). Etc.); Examples thereof include hydrides, hydroxides, carbonates, oxides, alkyl compounds and aryl compounds of these metals. These catalysts can be used alone or in combination of two or more. Among these catalysts, alkali metal hydrides such as sodium hydride are widely used. The proportion of the anionic polymerization catalyst is 0.001 to 3 mol%, preferably 0.005 to 2.5 mol%, and more preferably 0.01 to 2 mol% in the composition.

The anionic polymerization initiator is not particularly limited as long as it is a conventional initiator used in anionic polymerization of ω-lactam, and is, for example, N-acyllactam, isocyanates, triazines, carbodiimides, urea derivatives, isocyanurates. Examples include derivatives. These initiators can be used alone or in combination of two or more. Among these initiators, isocyanurate derivatives such as triallyl isocyanurate are widely used. The proportion of the anionic polymerization initiator is 0.0001 to 2 mol%, preferably 0.001 to 1.5 mol%, more preferably 0.01 to 1 mol% in the composition.

(Other additives)
In the composition of the present invention, as other additives, conventional additives such as conductivity-imparting agents (carbon black, etc.), organic or inorganic colorants, waxes, stabilizers (light stabilizers, heat stabilizers, etc.) Antioxidants, etc.), fillers, dispersants, preservatives, antifoaming agents, etc. may be further included. The ratio of the other additives is 10% by mass or less (for example, 0.01 to 10% by mass), preferably 5% by mass or less, based on the total composition.

[Polyamide molded product and its manufacturing method]
The polyamide molded product of the present invention is obtained by monomer-casting the monomer-casting composition (polymerizable lactam solution). As the monomer casting method, a conventional monomer casting method (monomer casting method or monomer casting method) in which a polymerizable lactam solution is cast into a mold such as a mold and heated to polymerize can be used.

Specifically, as a method for preparing a composition for monomer casting, an anionic polymerization catalyst is added to lactam that has been heated and melted to react and dissolve it, and then a nucleating agent and a toughness-imparting agent are added and mixed to polymerize. Immediately before, an anionic polymerization initiator may be further added and mixed. The temperature for heating and melting lactam is not particularly limited as long as it is equal to or higher than the melting point of lactam and lower than the polymerization temperature, and in the case of ε-caprolactam, for example, it is about 80 to 120 ° C. (particularly 90 to 110 ° C.). There may be. Further, after adding the anionic polymerization catalyst, the temperature is further raised in the range below the polymerization temperature (in the case of ε-caprolactam, the temperature is raised to, for example, 100 to 140 ° C, preferably 110 to 130 ° C), and then anionic polymerization is performed. Initiators may be added. Further, the mold is preferably preheated to a temperature equal to or higher than the temperature of the polymerizable lactam liquid and lower than the polymerization temperature.

The polymerization temperature in the mold may be equal to or lower than the melting point of the polyamide produced by the polymerization and varies depending on the type of the molded product, but in the case of ε-caprolactam, for example, about 150 to 210 ° C. (particularly 160 to 180 ° C.). Adjust to. The polymerization time can be selected from a range of several minutes to several hours depending on the type of the anionic polymerization catalyst and the anionic polymerization initiator and the polymerization temperature.

As the monomer casting method, for example, the methods described in JP-A-58-17914, JP-A-2002-302547, JP-A-2006-143999 and the like may be used.

The shape of the obtained polyamide molded product may be plate-shaped, rod-shaped, or the like. The plate-shaped or rod-shaped molded body may be machined into a predetermined shape.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The evaluation method of the polyamide molded product obtained in the examples is shown below.

[Crystallinity]
Using a differential scanning calorimeter (“DSC6200R” manufactured by Seiko Instruments Inc.), the temperature was raised from 40 ° C to 300 ° C under a nitrogen atmosphere at a heating rate of 10 ° C / min, and the obtained chart was melted. The crystallinity was calculated from heat.

[Spherulite diameter]
A thin section having a thickness of 5 μm was cut out from the round bars obtained in Examples and Comparative Examples, and a digital microscope (“VHX-5000” manufactured by KEYENCE CORPORATION) was used to obtain a crystalline state with transmitted light passing through a polarizing plate. Observed, the diameters of any 10 spherulites were measured and averaged.

[Tensile test]
Tensile strength, tensile modulus, and tensile elongation were measured according to ASTM D-638.

[Bending test]
Flexural strength and flexural modulus were measured according to ASTM D-790.

[Izod impact strength]
The Izod impact strength (notched) was measured according to ASTM D-256.

[Rockwell hardness]
Rockwell hardness was measured according to ASTM D-785.

[specific gravity]
Specific gravity was measured according to ASTM D-792.

[Example 1]
100 parts by mass (1,600 g) of substantially anhydrous ε-caprolactam (ε-caprolactam dehydrated under reduced pressure) was heated and melted to 100 ° C., and sodium hydride (solid content 63% by mass) of liquid paraffin was used as an anionic polymerization catalyst. 3 g was added and the reaction was dissolved. Subsequently, 0.1 parts by mass (1.6 g) of polyamide particles (“nylon 6 fine particles TR-2” manufactured by Toray Co., Ltd., average particle size 20 μm) and polyethylene glycol (“PEG # 20000” manufactured by Nichiyu Co., Ltd.), An average molecular weight of 20,000) and 1 part by mass (16 g) were added and mixed. This polymerizable lactam solution was heated to 120 ° C., 1.5 g of triallyl isocyanurate as an anionic polymerization initiator was quickly mixed, and then this was preheated to 140 ° C., and the internal dimensions were φ80 mm and the depth was 400 mm. It was poured into a cylindrical mold and polymerized in a furnace adjusted to 170 ° C. to produce a polyamide molded product.

[Example 2]
A polyamide molded product was produced in the same manner as in Example 1 except that the amount of polyethylene glycol added was 0.5 parts by mass (8 g).

[Example 3]
A polyamide molded product was produced in the same manner as in Example 1 except that the amount of polyethylene glycol added was 2 parts by mass (32 g).

[Example 4]
A polyamide molded product was produced in the same manner as in Example 1 except that the amount of the polyamide particles added was 0.01 parts by mass (0.16 g).

[Comparative Example 1]
A polyamide molded product was produced in the same manner as in Example 1 except that polyamide particles and polyethylene glycol were not added.

[Comparative Example 2]
A polyamide molded product was produced in the same manner as in Example 1 except that polyethylene glycol was not added.

[Comparative Example 3]
A polyamide molded product was produced in the same manner as in Example 1 except that polyamide particles were not added.

Table 1 shows the evaluation results of the polyamide molded products obtained in Examples and Comparative Examples.

It can be said that the toughness of the resin molded product (difficulty of cracking and chipping during processing and use) is high when the tensile elongation and the Izod impact strength are large. On the other hand, it can be said that the rigidity of the resin molded body (difficulty of deformation when receiving a force) is high when the tensile elastic modulus, bending elastic modulus, and Rockwell hardness are large.

As is clear from the results in Table 1, compared with Comparative Example 1 in which polyamide particles and polyethylene glycol were not added, in Examples 1 to 4 in which both were added, tensile strength, tensile modulus, bending strength, and bending elasticity were added. There is no big difference in the modulus and Rockwell hardness, and it can be said that the rigidity is almost the same, but the tensile elongation and the impact strength of the Izod are larger in Examples 1 to 4 than in Comparative Example 1, and Examples 1 to 1 It can be said that a molded body having very high toughness was obtained by 4.

On the other hand, in Comparative Example 2 in which polyamide particles were added but polyethylene glycol was not added, the tensile elongation was significantly reduced as compared with Comparative Example 1, and a molded product having high toughness could not be obtained.

In Comparative Example 3 in which only polyethylene glycol was added without adding polyamide particles, the tensile strength, tensile elastic modulus, flexural strength, flexural modulus, and Rockwell hardness were smaller than those in Comparative Example 1, resulting in a molded product having low rigidity. ing.

Polarized micrographs taken to measure the spherulite diameter are shown in FIGS. In Comparative Example 1 and Comparative Example 3 containing no nucleating agent, spherulite of 20 to 70 μm was observed, but in Example 1 and Comparative Example 2 to which the nucleating agent was added, the spherulite was very small.

The monomer casting composition of the present invention can be used as various engineering plastics, for example, automobile parts such as gears, rollers, and wheels, automated warehouse guide rollers, trolley wheels, bottle guides, steel plate transport rolls, and ships. It can be used as a cushioning material for wheels.

Claims (7)

A composition for monomer casting containing lactam, a nucleating agent and a toughness-imparting agent.
The nucleating agent contains polyamide particles having a melting point equal to or higher than the polymerization temperature of the lactam.
The toughness imparting agent, only contains a poly-ethylene glycol,
The ratio of the nucleating agent is 0.001 to 1 part by mass with respect to 100 parts by mass of the lactam.
A composition in which the ratio of the toughness-imparting agent is 0.1 to 5 parts by mass with respect to 100 parts by mass of the lactam and 50 to 5000 parts by mass with respect to 100 parts by mass of the nucleating agent . The number average molecular weight of 400 to 50,000 claim 1 Symbol placement of the composition of poly ethylene glycol. The composition according to claim 1 or 2 , wherein the average particle size of the polyamide particles is 1 to 100 μm. The composition according to any one of claims 1 to 3 , wherein the lactam is an anhydrous 5- to 20-membered ring lactam. The composition according to any one of claims 1 to 4 , further comprising an anionic polymerization catalyst and an anionic polymerization initiator. A method for producing a polyamide molded product by casting a monomer of the composition according to any one of claims 1 to 5 . A polyamide molded product containing a ring-opening polymer of lactam, a nucleating agent and a toughness-imparting agent.
The nucleating agent contains polyamide particles having a melting point equal to or higher than the polymerization temperature of the lactam.
The toughness imparting agent, only contains a poly-ethylene glycol,
The ratio of the nucleating agent is 0.001 to 1 part by mass with respect to 100 parts by mass of the lactam.
A molded product in which the ratio of the toughness-imparting agent is 0.1 to 5 parts by mass with respect to 100 parts by mass of the lactam and 50 to 5000 parts by mass with respect to 100 parts by mass of the nucleating agent .