WO1992010541A1

WO1992010541A1 - Polyacetal resin composition

Info

Publication number: WO1992010541A1
Application number: PCT/JP1991/001713
Authority: WO
Inventors: Yoshihisa Tajima; Keiichi Miyawaki
Original assignee: Polyplastics Co., Ltd.
Priority date: 1990-12-14
Filing date: 1991-12-13
Publication date: 1992-06-25
Also published as: BR9106208A; JP2602580B2; CA2072374A1; JPH04214756A; MX9102586A

Abstract

A polyacetal resin composition which is freed from delamination and other problems occuring in the molding and processing thereof caused by the polystyrene resin added for the purpose of improving various properties of polyacetal resin, and which gives a molded article with a good surface condition, reduced friction and abrasion, and lowered molding shrinkage. The composition comprises 55 to 95 parts by weight of a polyacetal resin, 43 to 3 parts by weight of a thermoplastic polystyrene resin and 20 to 2 parts by weight of a thermoplastic acrylic resin, as a third component, in a total amount of 100 parts by weight, wherein the combination of the polyacetal resin with the polystyrene resin is selected so as to satisfy a specified melt flow value.

Description

Description Polyacetal resin composition

[Industrial applications]

The present invention relates to a polyacetal resin composition. More specifically, a polyacetal composed mainly of a polyacetal resin and blended with a thermoplastic polystyrene resin and a thermoplastic acryl resin, has a good surface condition of the molded product, has low friction and wear, and has low molding shrinkage. The present invention relates to a resin composition.

[Conventional technology]

Boliacetal resin has excellent moldability, and has well-balanced mechanical properties, electrical properties, heat resistance, chemical resistance, friction and abrasion properties, and has excellent shochu fatigue properties as a plastic material. Therefore-It is used in a very wide range of fields as a representative engineering resin. However, with the expansion of application fields, there is a tendency for the required performance of resins to be increasingly sophisticated, and one of such demands is an improvement in molding shrinkage. In other words, polyacetal resin has high molding shrinkage due to its high crystallinity, which may be a problem for applications such as precision parts, thin parts, and large parts. In many cases, it is desired to improve the molding shrinkage. Further, with regard to friction and wear characteristics, polyacetal resins also belong to an excellent class, but further improvement is often desired.

In general, blending of other resins has been attempted as a method for improving various physical properties of polyacetal resin. The mixing of polystyrene resin For example, there are JP-B-44-946 and JP-A-64-38463, but the former is intended for 綞 -like substances, and according to the study of the present inventors, When the polymer mixture obtained by the above is used for molding, layer segregation and hybrid phenomena appear strongly, and have no practical value. In addition, the latter discloses that the use of a specific high-viscosity polystyrene resin is effective in solving such problems, but it is still not sufficient, and in particular, the viscosity of the composition is increased. There is a problem on the above <[disclosed this invention]

In view of the above problems, the inventors of the present invention have found that in the case of a polyacetal resin and an inexpensive thermoplastic polystyrene resin, a striped surface is formed on the surface of an injection-molded article due to poor dispersibility of the two and poor adhesion between resin phases. Eliminates the hindrance of the appearance of the cracking structure and the surface layer formation caused by friction, which impairs the friction and wear characteristics, which is one of the characteristics of polyacetal resin. As a result of intensive studies with the aim of obtaining a polyacetone resin composition having a smooth state, being excellent in abrasion and abrasion characteristics, and having an improved shrinkage ratio during molding, it has been found that the above-mentioned specific high distortion is obtained. By blending a specific thermoplastic acrylic resin as a third component in a specific amount without using polystyrene, the above-mentioned disadvantages can be solved and a good polyacetal resin molded product can be obtained. I discovered that, in which led to the present invention.

That is, the present invention comprises a polyacetal resin A, a thermoplastic polystyrene resin B, and a thermoplastic acryl resin C, wherein A is 55 to 95 parts by weight based on 100 parts by weight of the total amount of A, B, and C. Parts, B is 43 ~ 3 parts by weight, Wherein C is 20 to 2 parts by weight, and the melt flow value of the A and B components satisfies the following formula (1). Things.

MRF (B) / MRF (A) = l / 3 to 50 (1)

[However, MRF (A) is 190; measured by ASTM D-1238; Melt flow value of polyacetal resin A under a load of 2160g, MRF (B) is 200 by the same method, thermoplasticity under a load of 5000g Shows the root flow value of polystyrene resin B. ]

The Boriasetaru resin A component used in the present invention, Okishime styrene group (an CH ₂ 0-) in the polymer compound whose main structural unit, Po Li oxymethylene homo- Helsingborg mer, Okishimechiren other structural units in addition to groups , A turbo-limer, or a block-co-bolimer containing a small amount of, and the molecule may have not only a linear but also a branched or cross-linked structure. The degree of polymerization is not particularly limited, and may be any one having a moldability (for example, MRF (A) = 1.5 to 70 under the measurement conditions).

Next, as is known, the polystyrene resin of the component B used in the present invention is a resin obtained by a radical polymerization reaction or an ionic polymerization reaction mainly containing styrene, and is industrially a bulk polymerization, a solution polymerization, and a polymerization. Any of those obtained by suspension polymerization, emulsion polymerization and the like can be used. In addition, the polystyrene resin B of the present invention is mainly composed of styrene in addition to polystyrene as long as its properties are not significantly impaired, and has the ability to copolymerize reactive monomers such as other butyl compounds and gen compounds. , A rubber component may be introduced. In particular, polystyrene, polymethylstyrene, or a copolymer containing these as a main component, such as acrylate, methyl acrylate, acrylonitrile, butadiene, or chlorinated styrene, is preferably used. The component B has an MRF value (MRF (B> MRF (A))) for the component A that satisfies a value of 1/3 or more and 50 or less, preferably 1/2 to 25 under the above measurement conditions, The effect is sufficiently exhibited even without using a special high-fracture material, and there is no difficulty in molding due to an increase in the viscosity of the composition.

The acryl-based resin of the component C used in the present invention includes acrylic acid and acrylic acid esters (for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, Isopropyl acrylate, n-butyl acrylate, 1-n-hexyl acrylate, 1-n-octyl acrylate, methacrylic acid and methacrylic acid esters (eg, methyl methacrylate, methacrylic acid) Monoethyl, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isoptyl methacrylate, n-amyl methacrylate, n-octyl methacrylate, etc.) Polymers or copolymers of these, and vinyl compounds such as styrene, acrylonitrile, etc. It is a copolymer containing a diene compound such as styrene or isoprene as a comonomer. Of these, methyl methacrylate homopolymer or methyl methacrylate as a main component, other acrylates or other methacrylates, acrylate, methacrylate, styrene, Including Atari lonitril Copolymers are preferably used. Particularly preferred is a polymer having an ester of methacrylic acid and an aliphatic alcohol having 1 to 8 carbon atoms as a monomer. The molecular weight and the like of the component C are not particularly limited, but a low-viscosity linear one is preferred from the viewpoint of processability.

Next, the compounding amount of each component in the composition of the present invention is such that the polyacetal resin of A is 55 parts by weight or more when the total amount of the components A, B and C is 100 parts by weight. When the amount is less than 55 parts by weight, the original characteristics of the polyacetal resin are lost, and the mechanical strength and the like are particularly lowered, which is not preferable.

The polystyrene resin as the component B is 43 to 3 parts by weight, particularly preferably 35 to 5 parts by weight. If the component B is less than 3 parts by weight, the effect of improving the shrinkage during molding cannot be obtained, which is not preferable. The amount of the acrylic resin of the component C is 20 to 2 parts by weight, preferably 15 to 5 parts by weight, which is related to the amount of the component B. If the amount is too small, the boriacetal resin of the component A is used. The effect of improving the dispersibility of the styrene resin of the B component with respect to the above is not obtained, and the surface state of the molded article is poor, resulting in the formation of a surface layer, which is not preferable. If both components B and C are excessively large, the characteristics of the polyacetal resin will be diminished. Therefore, it is generally preferred that the total amount be 45 parts by weight or less.

As described above, simply melting and kneading the polystyrene resin with the boria acetal causes the dispersed polystyrene resin phase to appear as a striped phase hybrid structure on the surface of the injection molded product, and the surface layer is separated by friction. This. This is because the high-shear force generated near the surface layer during injection molding deforms the polystyrene-based resin phase to form a layered structure, which is combined with the polystyrene phase. It is considered that the surface contamination phenomenon occurs due to poor adhesion to the polyacetal phase. That is, in order to suppress layer formation due to deformation of both phases and to improve the adhesiveness of the two, a specific thermoplastic acryl-based resin is melt-kneaded at the same time, so that the acryl-based resin becomes polystyrene and polyacetal. It is understood that not only the surface layer is prevented by improving the adhesiveness of both phases by intervening at the interface with the phase, but also the effect of improving the surface condition of the molded product and improving the friction and wear characteristics is produced. You.

In addition, the polyacetal resin composition of the present invention may be made of a fiber form such as glass fiber or carbon fiber in accordance with the purpose of mechanical strength, heat resistance, dimensional stability, electrical properties, etc., in addition to the ABC component. And other fillers can be blended.

Further, to the composition of the present invention, an antioxidant, a heat stabilizer, a lubricant, a crystal nucleating agent, an ultraviolet absorber, a coloring agent, a release agent, and other ordinary additives can be added. Also, if a small amount of other thermoplastic resin is blended as a supplement, ¾ SLr 0

The composition of the present invention can be prepared by various known methods.At least, it is necessary to heat and melt in the presence of the three components A, B, and C, and to knead the mixture for 30 seconds or more. , And other components may be simultaneously used or may be separately added. Specifically, for example, after the components A, B, and C are uniformly mixed in advance by a mixer such as a tumbler or a mixer, the mixture is supplied to a single-screw or twin-screw extruder, melt-kneaded, and pelletized. After molding, it may be subjected to molding or may be directly molded.

The processing temperature is 5 to 100 ° C higher than the temperature at which the resin component melts. And in degrees, particularly preferably from 10 a to 60 ^e C above the melting point. If the temperature is too high, decomposition or abnormal reaction occurs, which is not preferable.

The melt-kneading time is at least 30 seconds to 15 minutes, and preferably 1 to 10 minutes.

The composition of the present invention comprising a polyacetal as a main component and a specific amount of a polystyrene-based resin and a polyacryl-based resin used in combination retains the characteristics of the polyacetal resin and disperses both as seen in a conventional polystyrene-based resin composition. There is no separation of the molded product surface due to poor affinity and affinity, there is no difficulty in molding process, it has a uniform and smooth surface condition, it has excellent friction and wear characteristics, and it is a disadvantage of polyacetal It reduces the shrinkage during molding, is effective in improving the dimensional accuracy of molded products, and is expected to expand its applications.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

Examples 1 to 5

As shown in Table 1, the proportions of (A) boria acetal resin (manufactured by Boriblastics Co., Ltd., Dyuracon), (B) polystyrene resin, and (C) polymethyl methacrylate (P title A) are shown in Table 1. (Weight), and the mixture was melt-kneaded at a setting temperature of 190 using a twin-screw extruder with an inner diameter of 30IM at a screw speed of 80 rpm, and pelletized. Next, the pellets were molded by an injection molding machine at a resin temperature of 200 to prepare test pieces, and the following physical property evaluation was performed. Tensile strength: Performed according to the method of ASTM D638.

Surface test: Adhesive tape was stuck on the surface of the tensile test piece, it was pulled off instantaneously, and the presence or absence of surface coating on the molded piece was visually judged. Shrinkage: One direction of ASTM tensile test piece The dimensions of the mold were measured accurately, and the difference (%) from the corresponding mold dimension was used as the shrinkage.

Friction and wear test: The specific wear on steel S55C was measured using a Suzuki-type friction and wear tester.

Table 1 shows the results.

Comparative Examples 1 to 6

Examples 1-5 except that the polyacetal resin alone, the polystyrene resin alone, and the combination of the polyacetal resin and the polystyrene two-component system, and the combination amount of the polymethylmethacrylate resin were outside the scope of the present invention. A composition was prepared in the same manner, molded, and evaluated. The results are shown in Table 1.

Example of implementation Comparative example

1 2 3 4 5 1 2 3 4 5 6

(A) Polyacetal (parts by weight) 85 80 60 87 70 100 90 90 80 89

(MRF = 9)

(B) Polystyrene (parts by weight) 5 10 30 10 15 100 10 20 10

(MRF-12)

(0 P thigh (weight part) 10 10 10 3 15 10 1 Surface wear No No No No No No No No Yes No Yes Yes Some specific wear (X10— ^s mm ^s / kgf-km) 30 22 17 20 25 32 15 40 205 52 35 Mold shrinkage (%) 1.7 1.5 1.0 1.8 1.1 2.2 0.5 2.0 2.0 1.9 2.0 Tensile strength (kg / cm ² ) 571 587 552 613 512 624 374 598 509 541 560

Examples 6 to 10, Comparative example? ~ Ten

Compositions were prepared in the same manner as in Examples 1 to 5 and Comparative Examples 1 to 6 except that the polystyrene resin was changed to styrene-acrylonitrile copolymer (AS), molded, and evaluated. The results are shown in Table 2.

Example of implementation Comparative example

6 7 8 9 10 1 7 8 4 9 10

(A) Polyacetal (parts by weight) 85 80 60 87 70 100 90 90 80 89

(MRF = 9)

(B) AS (parts by weight) 5 10 30 10 15 100 10 20 10

(MRF = 15)

(0 PMMA (part by weight) 10 10 10 3 15 10 1 surface and without None None None None None None None剝離There slightly Yes ratio wear amount (X10- ³謹^{3 / kgf -km) 48 44 35} 44 46 32 85 95 205 107 86 Mold shrinkage (%) 1.7 1.4 0.9 1.8 0.9 2.2 0.4 2.0 2.0 1.8 1.9 Tensile strength (kg / cm ² ) 615 654 701 686 623 624 813 652 509 684 661

Examples 11 to 15; Comparative Examples 11 to 14

The compositions were prepared, molded and evaluated in the same manner as in Examples 1 to 5 and Comparative Examples 1 to 6 except that the component (B) was changed to ABS resin. The results are shown in Table 3.

Example Example

11 12 13 14 15 1 11 12 4 13 14

(A) Polyacetal (heavy parts) 85 80 60 87 70 100 90 90 80 89

(MRF = 9)

(B) ABS (parts by weight) 5 10 30 10 15 100 10 20 10

(MRF = 5)

(0 P 瞧 (weight part) 10 10 10 3 15 10 1 Surface separation None None None None None None None None None Slight, None Surface stripes Specific wear (X10— ^s mm ³ / kgf-km) 94 91 100 86 109 32 155 122 205 209 120 Mold shrinkage (%) 1.8 1.3 0.9 1.8 1.1 2.2 0.4 1.8 2.0 1.6 1.8 Tensile strength (kg / cm ² ) 603 524 496 546 501 624 441 522 509 506 524

Examples 16 to 18, Comparative Examples 15 to 17

(C) Components in which the methyl group of the polymethyl methacrylate resin (PMMA) in Example 2 and Comparative Example 4 was changed to an ethyl group (PNC2MA), a component in which a normal octyl group was changed (PNC8MA), a normal dodecyl group ( PNC12MA) was prepared in the same manner as in Example 2 and Comparative Example 4 except that the composition was changed to PNC12MA), molded and evaluated. The results are shown in Table 4.

Example Comparative example

16 17 18 15 16 17

(A) Polyacetal (parts by weight) 85 80 80 90 90 90

(MRF = 9)

(B) Polystyrene (parts by weight) 10 10 10

Ys = 12)

(C) PNC2MA (weight part) 10 10

PNC8MA (weight) 10 10

PNC12MA (parts by weight) 10 10 exfoliation None None None None None None Ratio milling ^ S (Χ10 · ³ thigh ^{3 / kgf · km) 25 31} 51 215 243 237 molding shrinkage (%) 1.5 1.5 1.6 2.0 2.0 2.0 Difficult to pull (kg / cm ² ) 576 579 565 502 498 491 Example 19, Comparative Example 18

Using the same component A (MRF = 9) and component C as in Example 3, and using polystyrene having a different MRF as component B, a composition was prepared and molded in the same manner as in Example 3. As a result, when MRF (B) of component B = 4, that is, MRF (B) / MRF (A) = 4/9 (Example 19), the composition can be prepared and molded under the same conditions. Although almost the same characteristic values as in Example 3 were obtained, when MRF (B) = 2, that is, when MRF (B) / MRF (A) = 2/9 (Comparative Example 18), the composition was prepared under the same conditions. In addition, there was a rise in load at the time, and a shortage of charging occurred during molding, requiring a rise in temperature or injection pressure, and moldability was not sufficient.

Claims

2/10541

16

Claims. The resin is composed of polyacetal resin A, thermoplastic polystyrene resin B, and thermoplastic acrylic resin C. The amount of A is 55 to 95 parts by weight based on 100 parts by weight of the total amount of A, B, and C. , B is 43 to 3 parts by weight, C is 20 to 2 parts by weight, and the melt flow value of the A and B components satisfies the following equation (1): A polyacetal resin composition having a good quality.

MRF (B) XMRF (A) = l / 3 〜 50 (1)

(However, MRF (A) is the melt flow value of polyacetal resin A under a load of 2160 g at 190 C measured by ASTM D-1238, and MRF (B) is 200 according to the same method, and the thermoplastic ballistic under a load of 5000 g is used. Shows the melt flow value of lene resin B. ]

The thermoplastic polystyrene resin B is a copolymer resin containing polystyrene or polystyrene as a main component and acrylonitrile and Z or busugen and / or acrylic acid or acrylate. The polyacetal resin composition according to claim 1.

3. The boria cellulose resin composition according to claim 1, wherein the mature plastic acryl-based resin C is polymethyl methacrylate or a copolymer resin mainly containing the same.