JPH05220807A - Manufacture of long fiber-reinforced polyamide resin composition - Google Patents

Abstract

PURPOSE:To reduce a residual monomer and improve yield when a resin having compatibility with a polyamide resin is used as a coating resin by devising a combination of an anion polymerization catalyst and an activator. CONSTITUTION:An impregnating chamber 14 is supplied with liquefied lactams to which an anion polymerization catalyst composed of a sodium hydride single body is added, and liquefied lactams, to which an activator consisting of two- functional organic isocyanate is added, while both lactams are mixed at a specified ratio, and a mixed liquid is impregnated with long fiber-shaped reinforcing fibers 5 supplied continuously in the impregnating chamber 4. The reinforcing fibers 5 are introduced to the coating head section of a melt extruder through a nipple 11, a thermoplastic resin having a softening point of at least 120 deg.C or higher is melted and the outer circumferences of the impregnated reinforcing fibers are coated with the resin, a coating layer 14 is formed without a joint, the reinforcing fibers are introduced into a polymerizing chamber, and lactams in the coating layer 14 are anion-polymerized, and cut to specified length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a long-fiber-reinforced polyamide resin composition, and more particularly to a method for producing a polyamide resin after reaction with a small amount of residual monomers and a high yield.

[0002]

2. Description of the Related Art Various fiber-reinforced thermoplastic resin pellets made of a thermoplastic resin and reinforcing fibers and having excellent mechanical strength have been studied so far. The present applicant also studied a method for obtaining a fiber-reinforced polyamide resin composition easily in terms of equipment and handling, and has already filed as Japanese Patent Application No. 2-179064.

In the manufacturing method according to this application, long fiber-shaped reinforcing fibers are impregnated while continuously mixing lactams to which an anionic polymerization catalyst and an activator are added respectively, and immediately the outer periphery thereof is melted with a thermoplastic resin. After being coated with the above, it is supplied to a heating tank, an internal lactam is anionically polymerized in the presence of the catalyst and the activator, and then cut into a predetermined length to form a pellet.

The anionic polymerization catalyst used in this production method is selected from the alkali metals and alkaline earth metals used in the generally known alkali polymerization method for lactams. Further, the activator is selected from N-acyl lactam, which is a compound used in the known alkali polymerization method of lactams, organic isocyanate, acid chloride, acid anhydride, ester, urea derivative, carboimide and ketene. ..

According to this method, the fiber-reinforced thermoplastic resin pellets can be easily manufactured in terms of equipment and handling, and the resin pellets obtained are pellets having good wetting of the reinforcing fibers with the resin and excellent mechanical strength. ..

[0006]

In this method, when a resin compatible with the obtained polyamide resin composition is selected as the coating resin, the resin is compatible with the resin composition formed inside the coating layer. Therefore, the step of peeling off the coating layer after molding is unnecessary, and there is an advantage that the coating can be used as it is during the secondary processing.

However, depending on the type of these compatible coating resins, the anionic polymerization of lactams inside the coating layer is inhibited by decomposition gas generated during coating, and unreacted lactam or low molecular weight components (hereinafter referred to as residual monomer and There are many drawbacks. Since a composition containing a large amount of this kind of residual monomer causes depolymerization of the polyamide during the secondary processing, it is necessary to extract and separate the residual monomer immediately after the production, and the yield decreases if the amount of this component is large.

As a thermoplastic coating resin which does not inhibit the polymerization, there is, for example, a fluorine resin, but this fluorine resin has poor compatibility with a polyamide resin, and therefore the coating is peeled off during secondary processing. However, there is a drawback that the productivity is lowered due to the necessity.

The present invention is intended to solve the above problems, and its purpose is to devise a combination of an anionic polymerization catalyst and an activator so that when a resin compatible with a polyamide resin is used as a coating resin. The present invention provides a method for producing a long fiber-reinforced polyamide resin composition which has a small amount of residual monomers and can improve the yield.

[0010]

In order to achieve the above-mentioned object, the present invention provides a method of mixing a liquid lactam containing an anionic polymerization catalyst and a liquid lactam containing an activator at a predetermined ratio. The mixture liquid is supplied to the impregnation chamber, and the long fiber-shaped reinforcing fibers continuously supplied in the impregnation chamber are impregnated into the mixed solution, which is then introduced into the coating head portion of the melt extruder through a nipple, and the impregnation is performed. A thermoplastic resin having a softening point of at least 120 ° C. is melt-coated on the outer periphery of the reinforcing fiber in an inert gas atmosphere to form a seamless coating layer, which is then introduced into a heated polymerization chamber and the inside of the coating layer. After anionically polymerizing the lactam of, in the method for producing a long fiber-reinforced polyamide resin composition of cutting to a predetermined length, while using sodium hydride as the anionic polymerization catalyst,
A bifunctional organic isocyanate is used as the activator.

In the above production method, specific examples of the lactams used in the polymerization reaction include γ-butyrolactam, Σ-valerolactam, ε-caprolactam and ω.
-Enanthlactam, ω-capryllactam, ω-undecanolactam. These lactams may be used alone or in combination of two or more.

As the anionic polymerization catalyst, a simple substance of sodium hydride is selected from the compounds used in the known alkaline polymerization method of lactams, and 0.1 to 3 mol%, preferably 0.3 mol of lactams is selected. ~ 2.5mol%
Is added to and mixed with the monomeric lactams which are heated to be liquid (hereinafter referred to as liquid A).

As the activator, a bifunctional organic isocyanate is selected from the compounds used in the known alkaline polymerization method of lactams. Specific examples of the difunctional organic isocyanate include hexamethylene diisocyanate, 4,4-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, etc., and 0.2 to 3 mol%, preferably 0.5 to 3 mol% with respect to lactams. 2.0 mol% is added to and mixed with monomeric lactams which are liquefied by heating (hereinafter referred to as liquid B).

Inorganic fibers such as glass fibers and carbon fibers, and organic fibers such as polyester can be used as the reinforcing fibers.

The thermoplastic resin used for the coating layer is compatible with the polymerization product, has a softening point of at least 120 ° C. or higher in consideration of the temperature during anionic polymerization, and is a resin having a high resistance to the reaction solution. good. Specifically, polyamide resin, polyamide / polypropylene, polyamide / P
Alloy resins such as PO and polyamide / ABS can be covered.

[0016]

By using sodium hydride as the anionic polymerization catalyst in the liquid A, the catalytic activity can be stabilized. Further, by using a bifunctional organic isocyanate as an activator in the liquid B, the anionic polymerization rate is increased, and the polymerization reaction is stably performed without being affected by the polymerization inhibitor such as water and decomposition gas from the melt-coated resin. It can be completed, and the residual monomer amount of the obtained polyamide resin composition is greatly reduced as compared with the conventional one.

[0017]

Next, preferred embodiments of the present invention will be described. However, the present invention is not limited to the following examples.

Example 1. 1 and 2 show the whole and part of the manufacturing process according to the present invention. In the figure, it is heated to 80 ° C., tank 1 containing solution A mixed with ε-caprolactam as a monomer and 1 mol% sodium hydride added as an anionic polymerization catalyst, and also heated to 80 ° C. As an activator.
A tank 2 containing solution B containing 5 mol% of hexamethylene diisocyanate was prepared.

A mixing section 3 was provided below the tanks 1 and 2, and the mixing section 3 mixed the solutions A and B at a ratio of 1: 1 to prepare a reaction solution. The reaction liquid prepared in the impregnation chamber 4 connected to the lower part of the mixing unit 3 is continuously supplied, and the glass fibers 5 constituting the dried reinforcing fibers are guided into the impregnation chamber 4, and the glass fibers 5 The reaction solution was impregnated therein.

The surroundings of the impregnation chamber 4 are maintained at 80 ° C. and a nitrogen gas atmosphere is provided, a fiber guide hole 6 having an inner diameter of 2 mm is provided at the inlet of the impregnation chamber 4, and a solution impregnating portion 7 has a length of 500 mm and an inner diameter of The conical shape was narrowed from 10 to 3 mm, and a curved tube structure was used as shown in FIG. 2 so as to prevent backflow and retention of the reaction solution.

The outlet side of the impregnating portion 7 has a guide portion 9 having an inner diameter of 3 mm and is heated to 80 by a warm water connected to a pipe 10.
It is connected to the nipple 11 which is kept at ℃.

The viscosity of the reaction liquid when impregnating the glass fiber 5 was 10.5 centipoise. An outer diameter of 6 mm provided on the die head 30 of the melt extruder on the outer circumference of the reinforcing fiber 12 impregnated with the reaction liquid introduced to the nipple 11.
The molten nylon 6 resin was extruded from an annular die 13 having an inner diameter of 4 mm to form a coating layer 14, and extrusion coating was performed at a speed of 3 m / min.

The resin coating obtained in the above steps is immediately introduced into the cooling water tank 17 to cool the resin coating layer 14 on the surface, and then the polymerization tank 18 having a length of 30 m and controlled at 170 to 200 ° C. The reaction solution is continuously polymerized in the cooling water tank 19
After water cooling in the inside, it was taken up by a take-up machine 20, and then was cut into about 10 mm by a cutter 21 and pelletized.

This composition was subjected to Soxhlet extraction with methanol as a solvent to remove residual monomers. The amount of residual monomer was calculated from the weight of the polymerized polyamide after extraction with respect to the initial amount of lactam raw material. The composition after removal of residual monomers was fed to an injection molding machine having a screw diameter of 16 mm and an L / D of 28 to have an outer shape of 13.5 × 120 mm and a thickness of 3.
A 2 mm bending test piece was molded, and the bending strength, bending elastic modulus and Izod impact strength were measured. The molding conditions for the test piece were as follows: injection pressure 1200 Kg / cm ² , mold temperature 80.
℃, screw rotation speed 200rpm, back pressure 40Kg / c
m ² , cooling time 30 seconds, injection time 5 seconds. These results are collectively shown in the table below.

Example 2. Bifunctional 4,4 as activator
-A resin composition was obtained under the same production conditions as in Example 1 except that 0.5 mol% of diphenylmethane diisocyanate was used, and the residual monomer amount and mechanical strength were measured. These results are collectively shown in the table below.

Comparative Example 1. 1mol as anionic polymerization catalyst
% Metallic sodium and 1 mol% of monofunctional phenylisocyanate as an activator were used to obtain a resin composition under the same production conditions as in Example 1, and the residual monomer amount and mechanical strength were measured. These results are collectively shown in the table below.

Comparative Example 2. 1mol as anionic polymerization catalyst
% Sodium hydride and 1 mol% of monofunctional phenyl isocyanate as an activator were used to obtain a resin composition under the same production conditions as in Example 1, and the residual monomer amount and mechanical strength were measured. These results are collectively shown in the table below.

[0028]

[Table 1] As is clear from the above table, in both Examples 1 and 2, the residual monomer amount was greatly reduced to about 1/2 to 1/3 as compared with Comparative Examples 1 and 2, and the degree of polymerization was improved. , Izod impact value increased. This also suggests that when a combination of sodium hydride and a bifunctional organic isocyanate is used, it is less susceptible to polymerization inhibitors such as water and generated gas.

[0029]

INDUSTRIAL APPLICABILITY As described in detail in the above examples, according to the production method of the present invention, sodium hydride is used as the anionic polymerization catalyst in solution A, and bifunctional as an activator in solution B. By using these organic isocyanates in combination, the catalytic activity is stabilized, the anionic polymerization rate is increased, and the polymerization reaction is stably performed without being affected by the polymerization inhibitor such as water or decomposition gas from the melt-coated resin. Since the amount of residual monomer of the obtained polyamide resin composition can be reduced to a great extent as compared with the conventional one, this kind of long fiber reinforced polyamide resin composition can be produced with a higher yield than the conventional one. Further, since a resin having compatibility with the polyamide resin composition can be used as the coating resin, there is no need to remove the coating resin during the subsequent injection molding, and there is an advantage that productivity is improved.

[Brief description of drawings]

FIG. 1 is an overall explanatory view showing steps of a manufacturing method according to the present invention.

FIG. 2 is a detailed view of an essential part of FIG.

[Explanation of symbols]

 3 Mixing Chamber 4 Impregnation Chamber 5 Reinforcing Fiber (Glass Fiber) 14 Covering Layer 18 Polymerization Tank 20 Pulling Machine 21 Cutter 30 Die Head

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B29C 67/14 L 7188-4F C08G 69/18 MRQ 9286-4J // B29K 77:00 105: 08

Claims (1)

[Claims] 1. A liquid lactam added with sodium hydride as an anionic polymerization catalyst and a liquid lactam added with a bifunctional organic isocyanate as an activator are supplied to an impregnation chamber while being mixed at a predetermined ratio. The continuous liquid supplied in the impregnation chamber is impregnated with the long-fiber-shaped reinforcing fiber into the mixed liquid, which is then introduced into the coating head portion of the melt extruder through a nipple, and the outer periphery of the impregnated reinforcing fiber is introduced. A thermoplastic resin having a softening point of at least 120 ° C. is melt-coated to form a seamless coating layer, which is then introduced into a heated polymerization chamber to anionically polymerize the lactams inside the coating layer, and then a predetermined amount is obtained. A method for producing a long fiber-reinforced polyamide resin composition, which comprises cutting into a length.