JPH07179724A - Modified polyacetal resin composition - Google Patents

Abstract

PURPOSE:To obtain a resin composition, having a low specific gravity, excellent in affinity between resins and weld characteristics without deteriorating mechanical or thermal characteristics and useful as portable telephones, etc., by melt kneading a specific polyacetal resin composition with a prescribed amount of an acid anhydride-modified polyolefin-based resin, etc. CONSTITUTION:This resin composition is obtained by melt kneading (A) 80-100wt.% polyacetal resin with (B) 0.01-20wt.% polyisocyanate compound (a modified derivative) such as 4,4'-methylenebisphenyl isocyanate and (C) 0.01-3wt.% reactive promoting catalyst for isocyanates such as amines at a higher temperature than the melting point of the component (A) and then melt rekneading 100 pts.wt. resultant solidified polyacetal resin composition with (D) 1-100 pts.wt. acid anhydride-modified polyolefinic resin or acid anydride- modified PS-based resin prepared by modifying 100 pts.wt. polyolefinic or PS- based resin with 0.1-50 pts.wt. acid anhydride such as maleic anhydride at a higher temperature than the melting point of the component (A).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention improves the affinity between resins of a polymer blend composed of a polyacetal resin and a polyolefin resin or a polystyrene resin, and is excellent without impairing the mechanical and thermal properties of the polyacetal resin. The present invention relates to a resin composition exhibiting excellent weld characteristics and realizing low specific gravity.

[0002]

2. Description of the Related Art Polyacetal resins have excellent characteristics in mechanical and thermal characteristics, electrical characteristics, slidability, moldability, and dimensional stability of molded products. , Electrical equipment such as structural materials and mechanical parts,
Widely used in automobile parts and precision machine parts. However, in the current market where electric devices, precision machines, etc. are becoming lighter, thinner, shorter, and smaller, there is an increasing tendency to demand the weight reduction of structural materials and mechanical parts materials. The polyacetal resin is no exception, and in particular, the polyacetal resin has a high specific gravity, and there is a demand for a lighter weight polyacetal resin. In order to meet this expectation, for example, a method of blending a polyolefin resin or polystyrene resin having a low specific gravity with a polyacetal resin can be considered, but since the affinity between the added resin and the polyacetal resin is not good, it was simply melt-kneaded. It is said that dispersion failure occurs only by itself, appearance defects such as flow marks and surface layer peeling occur on the molded product, and the excellent properties of the polyacetal resin, particularly the weld property, are impaired due to insufficient interfacial bond strength between the two resins. There are drawbacks.
Therefore, attempts are being made to improve the affinity between the polyacetal resin and other resins.

[0003]

Therefore, as a result of diligent study on such points, the inventors of the present invention have found that a thermoplastic polyacetal resin is blended with an isocyanate and a reaction catalyst in advance (first stage melt kneading), and an acid is added to the composition. By adding an anhydride-modified polyolefin-based resin or acid anhydride-modified polystyrene-based resin, the affinity between the polyacetal resin and the polyolefin-based resin or polystyrene-based resin is improved, and the excellent mechanical and thermal properties of the polyacetal resin are improved. We succeeded in developing a low specific gravity molding resin material having excellent weld characteristics without loss, and completed the present invention. That is, the present invention relates to (A) a polyacetal resin of 80% by weight or more and less than 100% by weight, and (B) a polyisocyanate compound or a modified product thereof in an amount of 0.01 to 20% by weight and (C) an isocyanate reactivity promoting catalyst in an amount of 0.01 to 3%. (D) Acid anhydride-modified polyolefin resin or acid anhydride-modified polystyrene resin in 100 parts by weight of polyacetal resin composition (first-stage melt-kneading composition) solidified by melting and kneading wt% above the melting point of polyacetal resin It is a modified polyacetal resin composition (second-stage melt-kneading composition) obtained by melt-kneading 1 to 100 parts by weight of the resin again at a melting point of the polyacetal resin or higher.

The constituent components of the present invention will be described below. The polyacetal resin in the present invention is a thermoplastic resin containing a polymer compound having an oxymethylene unit (-CH ₂ O-) as a main repeating constitutional unit as a main component, and formaldehyde, trioxane, tetraoxane or the like by a usual method. Homopolymerized products, copolymers composed of two or more of these, or monomers and cyclic ethers such as ethylene oxide, propylene oxide, oxacyclobutane, and 1,3-dioxolane, β-propiolactone, γ-
A cyclic ester such as butyrolactone or a copolymer with a certain vinyl compound is used as the component (A). Further, the polyacetal resin may have a part of its molecular terminal converted to an ether bond, an ester bond, or the like. Further, part or all of the polyacetal resin is
For example, a polyacetal resin having a large hydroxyl group content produced by the method described below (hereinafter referred to as a hydroxyl-rich polyacetal resin) is more preferable, and in such a case, the effect of the present invention is more remarkable. In this case, the hydroxyl group content in the polyacetal resin is 30 mm.
Particularly preferable results can be obtained at ol / kg or more. As a method for producing the hydroxyl group-rich polyacetal resin, for example, when polymerizing trioxane with a cationic initiator such as BF ₃ , water, ethylene glycol, glycerin, a small amount of a compound containing a hydroxyl group such as glycidol is added. Although there are methods and the like, the manufacturing method is not particularly limited. Further, the degree of polymerization, the presence or absence of branching, homopolymer or copolymer, or copolymer type such as random, block or graft may be used. Also, the binding site of the hydroxyl group is not particularly limited.

The polyisocyanate compound or its modified product used as the component (B) in the present invention is a compound having an iso (thio) cyanate group in the molecule, and 1
It is a compound containing two or more iso (thio) cyanate groups in the molecule. Examples of component (B) include, for example, 4,4 ′
-Methylenebis (phenylisocyanate), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 1,
5-naphthalene diisocyanate, or diisothiocyanate corresponding to these and dimers or trimers thereof, further, any of the compounds in which the isocyanate group (-NCO) is protected in any form, etc. can be used. Considering various properties such as discoloration degree of melt processing, etc., or safety in handling, 4,4'-methylenebis (phenylisocyanate), isophorone diisocyanate, 1,5-naphthalene diisocyanate, 2,4-tolylene diisocyanate , 2,6-tolylene diisocyanate, 1,6-hexamethylene diisocyanate and dimers thereof,
A modified form (or derivative) such as a trimer is particularly preferable. (B)
The compounding amount of the component (A) must be in the range of 0.01 to 20% by weight with respect to 80% by weight or more and less than 100% by weight of the component (A).
When the content of the component (B) is less than 0.01% by weight, the compatibility between the acid anhydride-modified polyolefin-based resin or acid anhydride-modified polystyrene-based resin and the polyacetal resin, which will be described later, is insufficient, and when it exceeds 20% by weight, gelation occurs. Occurs, and the fluidity and the resin properties deteriorate, which is not preferable.

As the reactivity-promoting catalyst for isocyanate which is the component (C) of the present invention, any of organometallic compounds containing amines, Sn, Zn, Pb, etc., which are generally known as reaction catalysts for isocyanate, can be used. But you can
It is preferable to use a resin that does not adversely affect the polyacetal resin such as discoloration or decomposition. From this point of view, examples of amines as a preferable reaction catalyst include melamine and substituted melamine, and examples of organometallic compounds include zinc stearate and di-n-butyltin dilaurate. The blending amount of component (C) is 0.01 to 80% by weight or more and less than 100% by weight of component (A).
It is necessary to be in the range of 3 wt%. 0.01% by weight
If it is less, the action as a catalyst is not sufficient, and it is 3% by weight.
If it exceeds the range, discoloration of the polyacetal resin and deterioration of the resin properties occur, which is not preferable.

The component (D) of the present invention is an acid anhydride-modified polyolefin resin or acid anhydride-modified polystyrene resin obtained by modifying a polyolefin resin or polystyrene resin with an acid anhydride. Examples of the polyolefin-based resin used here include α-such as ethylene, propylene, butene, hexene, octene, nonene, decene, and dodecene.
Olefin homopolymers, random, block or graft copolymers of two or more of these, or 1,4-hexadiene, dicyclopentadiene, 5-
Non-conjugated dienes such as ethylidene-2-norbornene and 2,5-norbonadiene, conjugated diene components such as butadiene, isoprene and piperylene, α, β-unsaturated acids such as acrylic acid and methacrylic acid, or derivatives thereof such as esters, acrylonitrile , One or more of comonomer components such as aromatic vinyl compounds such as styrene and α-methylstyrene, vinyl esters such as vinyl acetate, vinyl ethers such as vinyl methyl ether and derivatives of these vinyl compounds. Examples thereof include random, block or graft copolymers, and the degree of polymerization thereof, the presence or absence of side chains or branches, the degree thereof, the composition ratio of the copolymers, and the like do not matter. On the other hand, as the polystyrene resin, styrene, α-methylstyrene,
Homopolymers of aromatic vinyl compounds such as vinyltoluene, p-tert-butylstyrene, p-hydroxystyrene and the like, or random, block or graft copolymers of two or more of these, or acrylic acid , Α, β-unsaturated acids such as methacrylic acid or derivatives thereof such as esters thereof, acrylonitrile, methacrylonitrile and derivatives thereof, vinyl esters such as vinyl acetate, vinyl ethers such as vinyl methyl ether and vinyl compounds thereof. Examples thereof include random, block or graft copolymers containing at least one kind of comonomer components such as derivatives, regardless of the degree of polymerization, presence or absence of side chains or branches, degree, copolymer composition ratio, etc. Absent. or,
As the acid anhydride used for modification, maleic anhydride, citraconic anhydride, itaconic anhydride, tetrahydrophthalic anhydride, nadic acid anhydride, methyl nadic acid anhydride, unsaturated carboxylic acid anhydrides such as allyl succinic anhydride, or One or more kinds selected from the derivatives are used. In addition, as the modification method, a method of adding an unsaturated carboxylic acid anhydride such as maleic anhydride or a derivative thereof when copolymerizing a polyolefin (or polystyrene) -based resin and copolymerizing the same is generally used. The manufacturing method is not limited. Here, the blending amount of both components is 100% based on the polyolefin (or polystyrene) resin.
0.1 to 50 parts by weight of acid anhydride, based on parts by weight, preferably
0.1 to 30 parts by weight is suitable. When the amount of the effective acid anhydride in the acid anhydride-modified polyolefin (or polystyrene) -based resin is too small, the affinity between the polyacetal resin and the polyolefin (or polystyrene) -based resin is not sufficiently improved. If the effect is not obtained and the amount is too large, gelation may occur, which may cause poor dispersibility or defective molding. The blending amount of component (D) is (A),
The amount is 1 to 100 parts by weight based on 100 parts by weight of the polyacetal resin composition (first stage melt-kneading composition) comprising the components (B) and (C). If the compounding amount of the component (D) is too low, the effect of the present invention will not be sufficiently exhibited, and if it is too large, the properties of the polyacetal resin will be impaired.

The present invention relates to a polyacetal resin (A) and an acid anhydride-modified polyolefin or acid anhydride-modified polystyrene.
In order to improve the compatibility with (D), polyisocyanate (B)
And its reaction catalyst (C) are kneaded with the polyacetal resin in advance, and the acid anhydride-modified polyolefin (or polystyrene) is melt-kneaded with this first-stage melt-kneaded composition. The weld characteristics of the product are improved. Regarding the cause of the effect of improving the weld characteristics in the present invention, by using a polyolefin (or polystyrene) modified with an acid anhydride, a reaction of an isocyanate with an acid anhydride and a reaction of an isocyanate with a polyacetal may result in a polyolefin (or polystyrene). It is presumed that the compatibility between) and polyacetal was improved, and in particular, the reaction rate-determining reaction between isocyanate and polyacetal could be improved by two-step extrusion and the use of a catalyst, but this is not always clear, and this is not clear. The present invention is not limited in any way. This can be confirmed by observing the fracture surface in 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 a general polyolefin (or polystyrene), it is recognized that a layered separation occurs in the welded portion. On the other hand, in the case of the composition of the present invention, compatibility,
The dispersibility was excellent and no layered separation was observed at the weld.

Further, the composition of the present invention may appropriately contain other polymers as long as the physical properties thereof are not impaired. In particular, the polyacetal resin, the polyolefin-based resin or polystyrene-based resin other than the component (D) of the present application shows a very good compatibility with the composition of the present invention, so that even if added in a considerably large amount, a problem such as peeling occurs. No
It does not impair the physical properties. In this case, the cost of the product can be reduced by adding the unmodified polymer to the composition of the present invention. During melt-kneading, if necessary, antioxidants, UV absorbers, photoprotectors, phosphite stabilizers, peroxide decomposers, basic auxiliaries, nucleating agents, plasticizers, lubricants, antistatic agents. Additives such as agents, flame retardants, and colorants may be added in arbitrary amounts within the range not impairing the physical properties of the present invention. The composition obtained by the present invention can be molded by a usual method.

[0010]

EFFECT OF THE INVENTION The composition obtained by the present invention has the improved properties of polyacetal resin and polyolefin (or polystyrene) type resin, and thus has excellent properties of polyacetal resin in terms of thermal properties and mechanical strength. Achieving a low specific gravity while maintaining the same, and providing a resin composition with good weld characteristics, without the appearance defect and surface peeling of the molded product due to the poor dispersion of the dispersed resin, many applications Application can be expected. In particular, the achievement of low specific gravity is expected to be used in fields such as handy-type video movies and mobile phones, which require weight reduction.

[0011]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Example 1 (A) 98.5% by weight of polyacetal resin, (B) 1% by weight of isophorone diisocyanate and (C) zinc stearate 0.5
The weight% was melt-kneaded with a 30 mm twin-screw extruder at a set temperature of 190 ° C. and a screw rotation speed of 100 rpm to pelletize. This was dried at 80 ° C for 2 hours or more, and then 100 parts by weight of the first-stage melt-kneaded composition (D) 100 parts by weight of a low-density polyethylene resin was modified with 3 parts by weight of maleic anhydride. 20 parts by weight of modified polyethylene was kneaded with a 30 mm twin-screw extruder at a set temperature of 190 ° C. and a screw rotation of 100 rpm to pelletize, and dried at 80 ° C. for 2 hours or more. The pellets were molded into test pieces by an injection molding machine, and the following evaluations were performed. The evaluation results are shown in Table 1. [Specific gravity] Measured according to ASTM D 792. [Surface layer peeling test] Cellophane tape was attached to the surface of the test piece and peeled off, and then the peeling condition was visually evaluated. If no peeling was observed, "○" was given, and if observed, "x" was given.
And [Confirmation of dispersibility] After the fracture surface of the molded article was immersed in a trichloroethane (room temperature) solution, the fracture surface was observed with an electron microscope, and the shape of the particle, the size of the particle, etc. were judged, and these were combined. Ranked as excellent, good, and bad. [Weld strength / extension] A weld test piece having a gate at both ends and a thickness of 2 mmt was used, and the measuring method was in accordance with ASTM D638. In addition, the same measurement was performed on the test piece having one gate, and the strength and the elongation depending on the presence or absence of weld were compared. Comparative Example 1 As shown in Table 2, a test piece was prepared and evaluated in the same manner as in Example 1 except that (C) zinc stearate was not added. Comparative Example 2 As shown in Table 2, a test piece was prepared in the same manner as in Example 1 except that (B) isophorone diisocyanate was not blended.
It evaluated similarly. Comparative Example 3 As shown in Table 2, a test piece was prepared by melt-kneading in one stage at a compounding ratio substantially similar to that of Example 1, and evaluated in the same manner.

Examples 2 and 3 As shown in Table 1, the amount of (D) maleic anhydride-modified polyethylene added was changed, and other sample preparation methods and the like were carried out in Example 1.
The evaluation was performed in the same manner as in. The composition and the evaluation results are shown in Table 1. Comparative Example 4 As shown in Table 2, a test piece was prepared and evaluated in the same manner as in Example 2 except that (C) zinc stearate was not blended. Comparative Example 5 As shown in Table 2, a test piece was prepared in the same manner as in Example 2 except that (B) isophorone diisocyanate was not blended.
It evaluated similarly. Comparative Example 6 As shown in Table 2, a test piece was prepared and evaluated in the same manner as in Example 3 except that (C) zinc stearate was not added.

Example 4 As shown in Table 1, (D) maleic anhydride-modified polystyrene was used, and other sample preparation methods and the like were performed in the same manner as in Example 1 and evaluated. The composition and the evaluation results are shown in Table 1. Comparative Example 7 As shown in Table 2, a test piece was prepared and evaluated in the same manner as in Example 4 except that (C) zinc stearate was not added.

Example 5 As shown in Table 1, the addition amount of (B) isophorone diisocyanate was changed, and 20 parts by weight of a polyacetal resin was further added and kneaded in the second stage kneading. Other sample preparation methods and the like were performed and evaluated in the same manner as in Example 1. The composition and the evaluation results are shown in Table 1. Comparative Example 8 As shown in Table 2, a test piece was prepared and evaluated in the same manner as in Example 5 except that (C) zinc stearate was not added.

Example 6 As shown in Table 1, kneading was performed using (C) di-n-butyltin dilaurate, and other sample preparation methods and the like were performed in the same manner as in Example 1 and evaluated. The composition and the evaluation results are shown in Table 1. Comparative Example 9 As shown in Table 2, a test piece was prepared in the same manner as in Example 6 except that (B) isophorone diisocyanate was not blended.
It evaluated similarly.

Examples 7 to 9 As shown in Table 1, the addition amount and type of the component (B) were changed,
Further, in the second-stage kneading, the addition amount of (D) maleic anhydride-modified polyethylene was changed and kneading was performed. Other sample preparation methods and the like were performed and evaluated in the same manner as in Example 1. The composition and the evaluation results are shown in Table 1. Comparative Example 10 As shown in Table 2, test pieces were prepared and evaluated in the same manner as in Example 7 except that zinc stearate (C) was not added. Comparative Example 11 As shown in Table 2, a test piece was prepared and evaluated in the same manner as in Example 8 except that (C) zinc stearate was not blended. Comparative Example 12 As shown in Table 2, a test piece was prepared and evaluated in the same manner as in Example 9 except that (C) zinc stearate was not blended.

[0017]

[Table 1]

[0018]

[Table 2]

Claims (5)

[Claims] 1. A (A) polyacetal resin 80% by weight or more 100
(B) Polyisocyanate compound or its modified product 0.01-
After 20% by weight and 0.01 to 3% by weight of (C) isocyanate reactivity promoting catalyst were melt-kneaded at a melting point of the polyacetal resin or higher, 100 parts by weight of the solidified polyacetal resin composition (first stage melt-kneading composition) ( D) A modified polyacetal resin composition (second-stage melt-kneaded composition) obtained by melt-kneading 1 to 100 parts by weight of an acid anhydride-modified polyolefin resin or an acid anhydride-modified polystyrene resin at a melting point of the polyacetal resin or higher. 2. The (B) polyisocyanate compound or its modified product is 4,4′-methylenebisphenyl isocyanate, isophorone diisocyanate, 1,5-naphthalene bisphenyl isocyanate, 1,6-hexamethylene diisocyanate, 2,4 − Tolylene diisocyanate, 2,6
-The modified polyacetal resin composition according to claim 1, which contains at least one selected from the group consisting of tolylene diisocyanate and dimers and trimers thereof. 3. A (C) isocyanate-reactivity-accelerating catalyst,
The modified polyacetal resin composition according to claim 1 or 2, which is an organometallic compound containing an amine or a metal selected from Sn, Zn, and Pb. 4. A (C) isocyanate reactivity promoting catalyst,
The modified polyacetal resin composition according to any one of claims 1 to 3, which is melamine, substituted melamine, zinc stearate or di-n-butyltin dilaurate. 5. The (D) acid anhydride-modified polyolefin-based resin or acid anhydride-modified polystyrene-based resin is obtained by modifying 100 parts by weight of a polyolefin-based resin or polystyrene-based resin with 0.1 to 50 parts by weight of an acid anhydride. The modified polyacetal resin composition according to any one of claims 1 to 4.