JP3167236B2 - Polyacetal resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention improves the affinity between resins of a polymer blend composed of a polyacetal resin and a polystyrene resin, and provides good weld properties without impairing the mechanical and thermal properties of the polyacetal resin. And a resin composition having reduced specific gravity.

[0002]

2. Description of the Related Art Polyacetal resins have excellent mechanical, thermal, electrical, slidability, moldability and dimensional stability of molded articles. Electrical equipment as structural materials and mechanical parts, etc.
Widely used for automotive parts, precision machine parts, etc. However, in the current market where electrical devices, precision machines, and the like are becoming lighter and thinner, there is an increasing tendency to reduce the weight of structural materials and materials for mechanical parts. The polyacetal resin is no exception. Particularly, the polyacetal resin has a high specific gravity and a lighter weight polyacetal resin material is required. In order to meet this expectation, for example, a method of blending a polystyrene resin having a small specific gravity with a polyacetal resin is conceivable.However, since the affinity between the added resin and the polyacetal resin is not good, simply melt-kneading alone results in poor dispersion. This results in defects such as poor appearance such as flow marks and surface layer peeling in the molded product, and inferior properties of polyacetal resin, particularly weld property, due to insufficient interfacial bond strength between the two resins. Therefore, in order to improve the affinity between the polyacetal resin and the polystyrene resin, there is known a method in which the ratio of the melt flow values of the polyacetal resin and the polystyrene resin is in a specific range (Japanese Patent Laid-Open No. 64-38463). However, they have not yet been sufficiently improved (particularly, weld characteristics).

[0003]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on such a point, and have found that a polyacetal resin is mixed with a polyisocyanate resin having an acid anhydride group and a polyisocyanate to form a polyacetal resin and a polystyrene-based resin. Improved the affinity with the resin, succeeded in developing a low specific gravity molding resin material with excellent weld properties without impairing the excellent mechanical and thermal properties of polyacetal resin, and completed the present invention Reached. That is, the present invention
(A) 100 parts by weight of a polyacetal resin, (B) 1 to 200 parts by weight of an acid anhydride-modified polystyrene resin, and (C) 0.01 to 10 parts by weight of a polyisocyanate compound or a modified product thereof. It relates to a composition.

[0004] The components of the present invention will be described below. The polyacetal resin in the present invention, a thermoplastic resin whose main component is polymeric compound which oxymethylene units (-CH ₂ O-) as the main repeating structural units, formaldehyde or trioxane, the tetraoxane like in a usual manner Homopolymerized, or a copolymer of two or more of these, or a monomer and a cyclic ether such as ethylene oxide, propylene oxide, oxacyclobutane, 1,3-dioxolan, β-propiolactone, γ-
A cyclic ester such as butyrolactone or a copolymer with a certain vinyl compound or the like is used as the component (A). Further, the polyacetal resin may have a part of its molecular terminal converted into an ether bond, an ester bond, or the like. Further, part or all of the polyacetal resin,
For example, a polyacetal resin having a large hydroxyl group content (hereinafter, referred to as a hydroxyl-rich polyacetal resin) produced by the following method is more preferable, and in such a case, the effect of the present invention is more remarkable. Also, in this case, the hydroxyl group content in the polyacetal resin is 30 mm
Particularly preferable results are obtained when the ol / kg or more is obtained. As a method for producing the wealth hydroxyl polyacetal resin, for example, when carrying out the polymerization of trioxane with cationic initiators, such as BF _3, water, ethylene glycol, glycerin, adding a small amount of compound containing a hydroxyl group such as glycidol There are methods and the like, but the production method is not particularly limited. The degree of polymerization, presence or absence of branching, homopolymer or copolymer, or copolymerization type such as random, block, graft, etc., does not matter. Also, the binding site of the hydroxyl group is not particularly limited.

[0005] The component (B) of the present invention is an acid anhydride-modified polystyrene resin obtained by modifying a polystyrene resin with an acid anhydride. As the polystyrene resin used here, styrene, α-methylstyrene, vinyltoluene,
Homopolymers of aromatic vinyl compounds such as p-tert-butylstyrene and p-hydroxystyrene and derivatives thereof, or random, block, or graft copolymers of two or more thereof, or acrylic acid, methacrylic acid, Derivatives of α, β-unsaturated acids or esters thereof such as acids, acrylonitrile, methacrylonitrile and derivatives thereof, vinyl esters such as vinyl acetate, vinyl ethers such as vinyl methyl ether and derivatives of these vinyl compounds, etc. Random, block, or graft copolymers comprising one or more of the comonomer components of the above, regardless of the degree of polymerization, the presence or absence or degree of side chains or branches, the copolymer composition ratio, etc. . Examples of the acid anhydride used for the modification include unsaturated carboxylic anhydrides such as maleic anhydride, citraconic anhydride, itaconic anhydride, tetrahydrophthalic anhydride, nadic anhydride, methylnadic anhydride, and allyl succinic anhydride. And one or more selected from derivatives thereof. As a modification method, a method of adding an unsaturated carboxylic anhydride such as maleic anhydride or a derivative thereof when polymerizing a polystyrene resin and copolymerizing the resin is generally used. It is not limited. here,
An appropriate amount of the two components is 0.1 to 50 parts by weight, preferably 0.1 to 30 parts by weight, of the acid anhydride based on 100 parts by weight of the polystyrene resin. If the amount of the effective acid anhydride in the acid anhydride-modified polystyrene-based resin is too small, the affinity between the polyacetal resin and the polystyrene-based resin is not sufficiently improved, so that the effects of the present invention cannot be obtained and the amount is too large. In such a case, gelation may occur, which may cause poor dispersibility or poor molding. The amount of component (B) is from 1 to 200 parts by weight, preferably from 5 to 70 parts by weight, per 100 parts by weight of component (A). If the amount of the component (B) is too low, the effects of the present invention cannot be sufficiently exerted. If the amount is too high, the properties of the polyacetal resin are impaired.

The polyisocyanate compound used as the component (C) in the present invention or a modified product thereof is a compound having two or more iso (thio) cyanate groups in the molecule or a modified product thereof, and is preferably a diisocyanate or a modified product thereof. A diisothiocyanate compound or a dimer or trimer thereof. Examples of the component (C) include, for example,
4,4'-methylenebis (phenyl isocyanate), 2,4
-Tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,5-naphthalene bis (phenyl isocyanate), isophorone diisocyanate,
1,5-Naphthalenediisocyanate or the corresponding diisothiocyanate and dimers and trimers thereof, as well as compounds in which the isocyanate group (-NCO) is protected in some form can be used. However, taking into account various properties such as the degree of discoloration of the melt treatment and the like, or safety in handling, 4,4′-methylenebis (phenylisocyanate), isophorone diisocyanate, 1,5-naphthalenebis (phenylisocyanate), Particularly preferred are 2,6-hexamethylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and their modified products (or derivatives) such as dimers and trimers. It is necessary that the amount of component (C) be in the range of 0.01 to 10 parts by weight per 100 parts by weight of component (A). 0.01
If the amount is less than 10 parts by weight, the compatibility between the acid anhydride-modified polystyrene and the polyacetal resin is not sufficient. If the amount is more than 10 parts by weight, gelation occurs, and the fluidity and resin properties are undesirably deteriorated.

The present invention improves the compatibility between the polyacetal resin (A) and the acid anhydride-modified polystyrene (B) by interposing the polyisocyanate (C), has good dispersibility, and is particularly suitable for forming a composition. The weld characteristics of the product are improved. In the present invention, in order to improve mechanical properties, particularly toughness, it is preferable to further blend a primary amine or a secondary amine as the component (D). Such primary amines and secondary amines are not particularly limited as long as they do not cause discoloration or decomposition of the polyacetal resin in melt-kneading with the polyacetal resin.From this viewpoint, the component (D) is melamine, Substituted melamines are particularly preferred. Also, the compounding amount of the component (D) is
(A) 0 to 5 parts by weight based on 100 parts by weight of the component. If the amount of the component (D) is too large, discoloration of the polyacetal parts by weight causes gelation, which is not preferable.

Further, in the present invention, it is possible to contain (E) another polystyrene resin other than the acid anhydride-modified polystyrene resin (B). (E) As a component,
Specifically, styrene, α-methylstyrene, vinyltoluene, p-tert-butylstyrene, homopolymers of aromatic vinyl compounds such as p-hydroxystyrene and derivatives thereof, or random consisting of two or more of these, Block, or a graft copolymer, and the like, and its degree of polymerization,
It does not matter whether or not there are side chains or branches, the degree of copolymerization, and the like. The amount of the component (E) is 0% based on 100 parts by weight of the component (A).
It must be in the range of ~ 100 parts by weight. In this case, the cost can be reduced by adding the component (E).
However, it is not preferable that the added amount of the component (E) is too large because physical properties are reduced.

The cause of the effect of improving the weld characteristics in the present invention is as follows. By using polystyrene modified with acid anhydride, the reaction between polyisocyanate and acid anhydride and the reaction between polyisocyanate and polyacetal cause polystyrene and polyacetal. It is presumed that the compatibility with the above has been improved, but it is not always clear, and the present invention is not limited at all. This can also be confirmed by observing the fracture surface at the weld portion of the molded product with an electron microscope. That is, in the case of a molded article of a composition of a polyacetal resin and general polystyrene, it has been recognized that laminar separation occurs in the weld portion. On the other hand, in the case of the composition of the present invention, the compatibility and the dispersibility were excellent, and no lamellar separation in the weld portion was observed.

The composition of the present invention is prepared by melt-mixing the above-mentioned components by various methods. For example, a method in which a predetermined amount of a polyacetal resin, an acid anhydride-modified polystyrene resin, and a polyisocyanate are melt-kneaded, and then cut into pellets after cooling, is particularly limited with respect to the compounding timing of each component and the method. Not something. At this time, if necessary, an antioxidant, an ultraviolet absorber, a light protectant, a phosphite stabilizer, a peroxide decomposer, a basic auxiliary, a nucleating agent, a plasticizer, a lubricant, an antistatic agent Any amount of additives such as a flame retardant and a colorant may be blended within a range that does not impair the physical properties of the present invention. Further, the polymer of the present invention can be appropriately blended with another polymer as long as the physical properties are not impaired. The composition obtained according to the present invention can be formed by a usual method.

[0011]

According to the composition obtained by the present invention, by improving the affinity between the polyacetal resin and the polystyrene resin, the composition can maintain low thermal properties and mechanical strength while maintaining the excellent properties of the polyacetal resin. The present invention provides a resin composition which achieves specific gravity and has good weld characteristics, and is free from poor appearance and surface peeling of a molded product due to poor dispersion of a dispersed resin, and can be expected to be applied to many uses. In particular, the achievement of low specific gravity is expected to be used in fields requiring light weight, such as handy type video movies and mobile phones.

[0012]

〔specific gravity〕

It was measured according to ASTM D792. [Surface Peeling Test] After a cellophane tape was attached to the surface of the test piece and peeled off, the state of peeling was visually evaluated. [Confirmation of dispersibility] After immersing the fracture surface of the molded article in a trichloroethane (room temperature) solution, observe the fracture surface with an electron microscope, judge from the shape of the particles, the size of the particles, etc. ,
Excellent, good, bad. [Tensile strength and elongation] Measured according to the method of ASTM D638. [Strength of Weld Strength and Elongation] A 2 mmt thick weld test piece having gates at both ends was used, and the measurement method was in accordance with ASTM D638.

Examples 2 to 6 As shown in Table 1, (B) maleic anhydride-modified polystyrene
Specimens were prepared and evaluated in the same manner as in Example 1 except that the amount of (B-1) added or the type or amount of (C) polyisocyanate was changed. Table 1 shows the composition and the evaluation results. Comparative Examples 1 to 4 Polyacetal resin alone or polyacetal resin (B)
A test piece was prepared in the same manner as in Example 1 by blending only the maleic anhydride-modified polystyrene (B-1), and evaluated in the same manner. Table 2 shows the composition and evaluation results. Comparative Example 5 (B) Instead of maleic anhydride-modified polystyrene (B-1),
A test piece was prepared and evaluated in the same manner as in Example 3 except that an unmodified polystyrene polymer was used. Table 2 shows the composition and evaluation results. Example 7 (B) Instead of maleic anhydride-modified polystyrene (B-1),
100 parts by weight of polystyrene resin was modified with 2 parts by weight of maleic anhydride (B) Maleic anhydride-modified polystyrene (B-2)
A test piece was prepared and evaluated in the same manner as in Example 3 except that (Sekisui Chemical Co., Ltd., Dairac D-700) was used. Table 1 shows the composition and the evaluation results. Comparative Example 6 Only a maleic anhydride-modified polystyrene (B-2) was blended with a polyacetal resin, and a test piece was prepared in the same manner as in Example 7 and evaluated in the same manner. Table 2 shows the composition and evaluation results. Example 8 As shown in Table 1, a test piece was prepared and evaluated in the same manner as in Example 2 except that melamine (D) was further added.
Table 1 shows the composition and the evaluation results. Examples 9 to 10 As shown in Table 1, test pieces were prepared and evaluated in the same manner as in Example 8, except that the type of (B) maleic anhydride-modified polystyrene or (C) polyisocyanate was changed. Table 1 shows the composition and the evaluation results. Comparative Example 7 As shown in Table 2, a test piece was prepared in the same manner as in Example 8 except that (C) isophorone diisocyanate was not blended.
It was evaluated similarly. Table 2 shows the composition and evaluation results. Example 11 As shown in Table 1, (E) polystyrene resin (Daicel
A test piece was prepared and evaluated in the same manner as in Example 9 except that R80 (Chemical Industry Co., Ltd.) was blended. Table 1 shows the composition and the evaluation results. Comparative Example 8 As shown in Table 2, a test piece was prepared in the same manner as in Example 11 except that (C) isophorone diisocyanate was not blended.
It was evaluated similarly. Table 2 shows the composition and evaluation results.

[0014]

[Table 1]

[0015]

[Table 2]

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 2/00-2/38 C08L 59/00-59/04

Claims (6)

(57) [Claims] (A) 100 parts by weight of a polyacetal resin, (B) 1 to 200 parts by weight of an acid anhydride-modified polystyrene resin, (C) 0.01 to 100 parts by weight of a polyisocyanate compound or a modified product thereof.
A polyacetal resin composition containing 10 parts by weight. (2) The acid anhydride-modified polystyrene resin is (B)
The polyacetal resin composition according to claim 1, wherein 100 parts by weight of a polystyrene resin is modified with 0.1 to 50 parts by weight of an acid anhydride. (C) The polyisocyanate compound or a modified product thereof is 4,4'-methylenebis (phenylisocyanate), isophorone diisocyanate, 1,5-naphthalenebis (phenylisocyanate), 1,6-hexamethylenediisocyanate, The polyacetal resin composition according to claim 1 or 2, which is at least one selected from the group consisting of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and dimers and trimers thereof. 4. The polyacetal resin composition according to claim 1, further comprising (D) a primary amine or a secondary amine. 5. The polyacetal resin composition according to claim 4, wherein (D) the primary amine or the secondary amine is melamine. 6. The polyacetal resin composition according to claim 1, further comprising (E) another polystyrene resin.