JPH093264A - Polyethylene resin composition - Google Patents

Abstract

PURPOSE: To obtain a polyethylene resin composition excellent in friction properties, high in mechanical strength, capable of shortening a molding cycle and useful for caps, etc., by alloying a specific branched polyacetal resin with the base of the polyethylene resin. CONSTITUTION: This polyethylene resin composition is obtained by blending (A) 100 pts.wt. polyethylene resin, (B) 3-100 pts.wt. branched polyacetal resin obtained by polymerizing (i) 99.88-85.00wt.% trioxane, (ii) 0.1-10wt.% cyclic ether and/or cyclic formal and (iii) 0.02-5wt.% diglycidyl compound. Moreover, it is preferable to blend (C) 0.01-15 pts.wt. polyisocyanate or its modified compound and (D) 0.1-30 pts.wt. modified polyethylene having active hydrogen group capable of reacting with the isocyanate group. Further, the component (ii) is preferably a compound of formula I (R<1> to R<4> are each H, an alkyl, etc.; R<5> is methylene, etc.; p is 0-3 integer) and the component (iii) is preferably a compound of formula II (m is 2-5 integer).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene resin composition based on polyethylene resin, which is obtained by alloying a specific branched polyacetal resin, has excellent friction characteristics, high mechanical strength, and can shorten the molding cycle. It is about. More specifically, shortening the molding cycle without impairing the toughness of polyethylene resin,
The present invention provides a polyethylene resin composition having improved mechanical strength and elastic modulus as well as excellent friction and wear characteristics. The polyethylene resin composition of the present invention is suitable for caps formed by injection molding and tube containers formed by extrusion molding. It is used.

[0002]

2. Description of the Related Art Polyethylene resin is inexpensive and lightweight, and is excellent in electrical properties, chemical properties, melt stability, etc., and therefore, containers, various films, tubes, sheets. Widely used in various fields as tapes, coating materials, etc. However, since the surface hardness is low, it is easily scratched, and the rigidity and elastic modulus are low, and
It has the drawback of poor friction and wear properties. Therefore, it could not be sufficiently used in a portion (for example, a sliding member) where such characteristics are required. In order to improve these points, a method of blending various fillers such as glass fibers or a lubricant such as fatty acid ester and silicone oil has been attempted. However, the compounding of the filler has a problem that molding cannot be performed in applications such as thin-walled molded articles that require fluidity. On the other hand, although the addition of a lubricant is recognized to have some improvement in friction and wear properties, there is a problem that the surface hardness is further lowered. Therefore, blending with a tough resin represented by a polyacetal resin or a polyester resin has been attempted. However, the polyethylene resin and these compounded resins are poorly mixed, resulting in poor dispersion by simply melt-kneading and not obtaining toughness, as well as the appearance of the surface of the molded product due to surface layer peeling or flow marks. There are problems such as damage, and it has not been put to practical use.

[0003]

[Means for Solving the Problems] As a result of intensive studies by the present inventors in order to solve the above problems, as a result of surface layer peeling and flow marks when a polyethylene resin is blended with a polyacetal resin, high shear during molding is observed. We found that it occurs because the polyacetal resin of the domain is stretched from particles to fine needles by force, and by making the polyacetal resin a branched structure, it will not be stretched into fine needles even under high shear during molding. Succeeded in Further, they found that the molding cycle of the polyethylene resin can be shortened by alloying with the polyacetal resin, and completed the present invention. That is, the present invention provides (A) polyethylene resin 100
Branched polyacetal resin obtained by polymerizing (B) 99.88 to 85.00% by weight of trioxane, 0.1 to 10% by weight of cyclic ether and / or cyclic formal, and 0.02 to 5% by weight of diglycidyl compound in parts by weight. The present invention relates to a polyethylene resin composition containing 3 to 100 parts by weight.

Hereinafter, the raw material compounds necessary for forming the polyethylene resin composition of the present invention will be described in detail in order. First, the (A) polyethylene resin of the present invention is a polymer containing ethylene as a main component, and has a content of ethylene of 100 to 70 mol%. Ethylene component
If it is less than 70 mol%, the mechanical strength is greatly reduced, which is not preferable. Further, the copolymerization component is propylene, butylene,
Penten and the like.

The branched polyacetal resin used as the component (B) means, when blended with a polyethylene resin,
It is important that the particles are not elongated into fine needles even under shearing during molding, and for this reason the molecular structure is not linear but has a branched (or crosslinked) structure. (B) Trioxane and comonomer, which are the main monomers constituting the branched polyacetal resin, are well-known substances conventionally used in the production of polyacetal resin.
That is, trioxane is a cyclic trimer obtained from formaldehyde. The cyclic ether and cyclic formal as the comonomer are compounds represented by the following general formula (1).

[0006]

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[In the formula, R ¹ , R ² , R ³ and R ⁴ represent a hydrogen atom, an alkyl group or an alkyl group substituted with a halogen, and may be the same or different. R ⁵ is a methylene group, an oxymethylene group, a methylene group substituted by an alkyl group or a halogenated alkyl group, or an oxymethylene group (in this case, p represents an integer of 0 to 3), or a formula- (CH ₂ ) ₄ -OCH _2- or-(O-CH ₂ -CH ₂ ) _q -OCH ₂
It means a divalent group represented by-(wherein q represents an integer of 1 to 4). The alkyl group has 1 to 5 carbon atoms,
1 to 3 hydrogens may be replaced by halogen atoms, especially chlorine atoms. Examples of such a cyclic ether or cyclic formal include epichlorohydrin, ethylene oxide, 1,3-dioxolane, diethylene glycol formal, 1,4-
Butanediol formal, 1,3-dioxane, propylene oxide and the like can be mentioned. Furthermore, cyclic esters such as β-propiolactone and vinyl compounds such as styrene or acrylonitrile are also used. Particularly preferred cyclic ethers and cyclic formal are one or more selected from ethylene oxide, dioxolane, trioxeban, and 1,4-butanediol formal. The amount of cyclic ether or cyclic formal used is 0.1 to 10% by weight, preferably 0.3 to 5%, based on the total amount of mixed monomers.
% By weight. If the amount is less than 0.1% by weight, the thermal stability, which is a characteristic of polyacetal resin, is insufficient, and if it exceeds 10% by weight, not only the mechanical strength decreases but also the manufacturing itself becomes difficult, and the improvement of properties by alloying I can not expect it. Next, the diglycidyl compound that causes branching in the polyacetal resin, which is a feature of the present invention, will be described.
The diglycidyl compound used for the production of the polyacetal copolymer of the present invention is an aliphatic ether having two glycidyl groups at the ends, and preferably the compound represented by the following general formula (2) or (3) is used.

[0008]

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Examples of the diglycidyl compound represented by the above formula (2) or (3) include diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, butanediol diglycidyl ether, and the like. Butanediol diglycidyl ether is particularly preferable. Is. The amount of the diglycidyl compound used is 0.02 to
It is 5.0% by weight, preferably 0.1 to 3.0% by weight. 0.02
If the amount is less than wt%, peeling or the like will occur during alloying with the polyethylene resin, and if the amount is more than 5.0 wt%, excessive crosslinking reaction or the like will occur during polymerization, making it difficult to manufacture itself. The mechanical strength and the like are remarkably reduced, which is not preferable.

Polymerization of such a polyacetal copolymer is
It may be carried out according to the polymerization of a trioxane copolymer which is generally well known. That is, a cation active catalyst is generally used as the catalyst. Specific examples of such catalysts include Lewis acids, particularly halides such as boron, tin, titanium, phosphorus, arsenic and antimony, such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride and pentapentane. Compounds such as phosphorus fluoride, arsenic pentafluoride and antimony pentafluoride, and complex compounds or salts thereof, protic acids such as trifluoromethanesulfonic acid, perchloric acid, esters of protic acids, especially perchloric acid and lower aliphatic alcohols. An ester of perchloric acid (for example, perchloric acid tertiary butyl ester), an anhydride of a protic acid, particularly a mixed anhydride of perchloric acid and a lower aliphatic carboxylic acid (for example, acetyl perchlorate), or an isopoly acid, a heteropoly acid (for example, Phosphomolybdic acid), or triethyloxonium hexafluorophosphate, triphenyl Chill hexafluoro ARUZE diisocyanate, acetyl hexafluoro borate and the like. Among them, boron fluoride or a coordination compound of boron fluoride and an organic compound (for example, ethers) is the most common and suitable. The polymerization reaction may be batch type, continuous type, or any of solution polymerization, melt bulk polymerization, etc., but a method of using a liquid monomer to obtain a solid powdery bulk polymer as the polymerization proceeds It is common. In this case, an inert liquid medium can coexist as necessary. The amount of the (B) branched polyacetal resin added is 3 to 100 parts by weight, preferably 5 to 70 parts by weight, based on 100 parts by weight of the (A) polyethylene resin. If this amount is less than 3 parts by weight, the mechanical strength and friction and wear properties are not sufficiently improved, and if it exceeds 100 parts by weight, the branched polyacetal resin partially forms a continuous phase in the polyethylene resin, which is a feature of the present invention. The particle dispersion of the domain is not achieved, and problems such as peeling occur.

In the present invention, the above-mentioned (B) branched polyacetal resin is used as a domain to suppress the layered dispersion in the vicinity of the surface layer even under shearing during molding, but in the present invention, the affinity at the matrix-domain interface is further improved. Therefore, it is more preferable to blend a polyisocyanate or a modified product thereof and a modified polyethylene having an active hydrogen group capable of reacting with an isocyanate group. Hereinafter, the polyisocyanate or a modified product thereof and a modified polyethylene having an active hydrogen group capable of reacting with an isocyanate group will be described. First, the polyisocyanate compound or a modified product thereof is a compound having an iso (thio) cyanate group in the molecule,
It is a compound containing two or more iso (thio) cyanate groups in one molecule. For example, 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 their corresponding diisothiocyanates and their dimers, and tris. Polymer, further isocyanate group (-NCO)
Can be used in any form, but various properties such as the degree of discoloration such as melt processing, or
Considering 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 modified products (or derivatives) such as dimers and trimers thereof are particularly preferable. The amount of polyisocyanate or its modified product is 0 based on 100 parts by weight of (A) polyethylene resin.
It must be in the range of 01 to 15 parts by weight. The amount
If it exceeds 15 parts by weight, gelation occurs and the fluidity and resin properties are deteriorated, which is not preferable. Next, the modified polyethylene having an active hydrogen group capable of reacting with an isocyanate group is an active hydrogen group capable of reacting with the isocyanate group in the molecule and binding thereto, that is, a hydroxyl group, a carboxyl group, 1
It is a modified polyethylene containing a primary or secondary amino group, an amide group and the like. Examples of the method for producing the modified polyethylene having an active hydrogen group include a method of introducing a monomer having an active hydrogen group during polymerization and a method of oxidatively decomposing polyethylene. The active hydrogen group is particularly preferably an acrylic acid group or a hydroxyl group, and its modification amount is preferably 0.1 to 10% by weight based on polyethylene. Modified amount 0.1% by weight
If it is less than 10% by weight, the effect of increasing the interfacial affinity between the matrix and the domain is not sufficient, and if it exceeds 10% by weight, gelation tends to occur, which is not suitable for the present invention. The average molecular weight of the modified polyethylene is not particularly limited, but a relatively low molecular weight is preferable, and an average molecular weight of 5,000 to 100,000 is particularly preferable in order to facilitate uneven distribution at the matrix-domain interface. Further, the main chain of the modified polyethylene may be a copolymer obtained by copolymerizing propylene, butene, hexene, etc. in addition to the polyethylene homopolymer,
It is desirable that the ethylene content be 80 mol% or more. The amount of the modified polyethylene having an active hydrogen group capable of reacting with the isocyanate group is 0.1 to 30 parts by weight, and if it exceeds 30 parts by weight, gelation and thickening occur, which is not preferable.

Further, the composition of the present invention may optionally contain additives such as an antioxidant, an ultraviolet absorber, a nucleating agent, a plasticizer, a lubricant, an antistatic agent, a flame retardant and a colorant. You may mix | blend arbitrary amounts in the range which does not impair the physical property of this invention. The composition obtained by the present invention can be molded by a usual method.

[0013]

EFFECT OF THE INVENTION The composition obtained by the present invention comprises a polyethylene resin and a polyacetal resin having a branched structure, so that the polyethylene resin retains the moldability and the chemical resistance while maintaining the thermal properties, mechanical strength, The friction characteristics are improved, and further, peeling of the surface layer and deterioration of the weld characteristics caused by the conventional alloying are suppressed, and application to many uses can be expected.

[0014]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Production example (synthesis of branched polyacetal resin B-1) Two circles with an inner diameter of 80 mm have a cross-section where some circles overlap, and an effective length
A continuous mixing reactor consisting of a barrel with a heat transfer medium on the outside of 1.3 m and two rotating shafts with multiple paddles that mesh with each other inside was used.
Passing hot water at ℃, rotate the two rotating shafts in different directions at a speed of 100 rpm. Continuously supplied at the same rate, at the same time, to the same place, a cyclohexane solution of dibutyl etherate of boron trifluoride was continuously added in a predetermined amount to perform copolymerization, and the reaction mixture discharged from the other end was Immediately, it was poured into water containing 0.1% of triethylamine to deactivate the polymerization catalyst. Next, the polymer was washed with acetone and then air-dried for stabilization to obtain a branched polyacetal copolymer (MI = 2.0). Reference Example (Synthesis of polyacetal copolymer B'-1) 96.95% by weight of trioxane, 3.0% by weight of dioxolane,
Polymerization was carried out in the same manner as in Production Example using a trioxane mixture containing 0.05% by weight of methylal, and a substantially linear polyacetal copolymer (MI = 2.2) was obtained through a stabilization process.

Examples 1 to 4 100 parts by weight of a polyethylene resin (manufactured by Mitsui Petrochemical Co., Ltd., low density polyethylene, Mirason 403P: A-1) was blended with the branched polyacetal resin B-1 synthesized above in the amount shown in Table 1. Then
30mm twin-screw extruder, setting 200 ℃, screw rotation 10
The mixture was melt-kneaded at 0 rpm and pelletized. Next, the pellets were molded into test pieces by an injection molding machine, and the following evaluations were performed. Table 1 shows the evaluation results. <Tensile strength (weld)> With gates at both ends, thickness 2
mm weld test pieces were used, and the measurement method was in accordance with ASTM D-638. In addition, the same test was performed on the one-gate test piece to compare the strengths with and without welds. <Flexural modulus> Using a test piece with a thickness of 1/4 inch, ASTM
The flexural modulus was measured by D-790. <Surface Layer Peeling Test> Cellophane tape was attached to the surface of the test piece and peeled off, and then the peeling state was visually observed, and the evaluation was performed according to the following five grades. ◎… No peeling at all ○… Slight peeling at all △… Slight peeling at all × ・ ・ ・ Peeling off more than half of the pasted surface ×× …… Peeling at all pasted surface <Limit molding cycle> Mold Temperature 45 ℃, cylinder temperature 20
An Izod test piece corresponding to ASTM D-256 was molded at 0 ° C, and the injection-cooling time required for the test piece to be released from the mold was combined to form a limit molding cycle. <Friction characteristics> Using Suzuki type friction and wear test (contact area 2.0 cm ² ), mating material metal (steel, S45C), linear velocity 100 mm / sec
The amount of resin abrasion was measured by sliding for 24 hours under a surface pressure of 2.5 kg / cm ² .

Examples 5 to 6 In addition to Example 1 (or 2), isophorone diisocyanate trimer and acrylic acid group-containing polyethylene (acrylic acid group-containing PE; Polybond 1009 manufactured by Uniroyal Chemical)
Was blended in the amounts shown in Table 1, and samples were prepared and evaluated in the same manner. Example 7 A sample was prepared and evaluated in the same manner as in Example 1 except that high-density polyethylene (Mitsui Petrochemical Co., Ltd., Hi-Zex 2100J: A-2) was used as the polyethylene resin. Example 8 In addition to Example 7, isophorone diisocyanate trimer and acrylic acid group-containing polyethylene (acrylic acid group-containing P
E: Polybond 1009 manufactured by Uniroyal Chemical Co., Ltd. was blended in an amount shown in Table 1, and a sample was prepared and evaluated by the same method. Comparative Example 1 As shown in Table 2, the polyethylene resin A-1 used in Example 1 was molded as it was and evaluated. Comparative Examples 2 to 4 Samples were prepared in the same manner as in Example 1, 2 or 5 except that the substantially linear polyacetal resin B'-1 obtained in Reference Example was used instead of the branched polyacetal resin B-1. ,evaluated. Comparative Example 5 The polyethylene resin A-2 used in Example 7 was molded as it was and evaluated. Comparative Example 6 Example 8 was repeated except that the substantially linear polyacetal resin B′-1 obtained in Reference Example was used instead of the branched polyacetal resin B-1.
Samples were prepared and evaluated in the same manner as in.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

As is apparent from the above description and Examples,
The composition of the present invention suppresses the peeling of the surface layer as seen in the conventional blending of a polyethylene resin and a polyacetal resin, and has improved mechanical strength, moldability and friction characteristics while maintaining the versatility of the polyethylene resin. Therefore, its application is expected to expand.

Claims (3)

[Claims] 1. A) 100 parts by weight of a polyethylene resin, (B) 99.88 to 85.00% by weight of trioxane, and 0.1 to 10
% By weight of cyclic ether and / or cyclic formal;
A polyethylene resin composition comprising 3 to 100 parts by weight of a branched polyacetal resin obtained by polymerizing 02 to 5% by weight of a diglycidyl compound. 2. The polyethylene resin composition according to claim 1, wherein the diglycidyl compound of the branched polyacetal resin (B) is an alkylene oxide diglycidyl ether. 3. The composition according to claim 1, further comprising 0.01 to 15 parts by weight of polyisocyanate or a modified product thereof and 0.1 to 30 parts by weight of modified polyethylene having an active hydrogen group capable of reacting with an isocyanate group. A polyethylene resin composition comprising: