JP2000230094A - Covering material for pipe fitting and pipe fitting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a covering material for pipe fitting excellent in moldability and also in impact resistance under cold- or heat-resistant atmosphere. SOLUTION: The covering material comprises (1) a vinyl chloride resin and (2) a graft copolymer formed by graft-copolymerizing a vinyl monomer to a rubber polymer with an average particle size of 260 nm or more. The rubber polymer may preferably include butadiene polymers and/or styrenebutadiene polymers, while the vinyl monomer may embrace methyl methacrylate and/or styrene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe joint covering excellent in formability and impact resistance in a cold and heat resistant atmosphere.

[0002]

2. Description of the Related Art A metal pipe joint used for a buried pipe or the like can be prevented from being oxidized or corroded on its inner and outer peripheral surfaces by coating it with a resin. In particular, vinyl chloride resin is widely used as a coating material for pipe joints used for connecting pipes such as connecting pipes and bent pipes and tubular molded bodies. However, the vinyl chloride resin has a disadvantage that it is brittle against impact.

In order to remedy this drawback, various types of graft polymers obtained by graft polymerization of a rubber polymer such as butadiene rubber or the like or a mixture of two or more vinyl monomers such as styrene or methyl methacrylate. It has been proposed to mix a copolymer with a vinyl chloride resin as a reinforcing agent. Among the graft copolymers, a methyl methacrylate-butadiene-styrene copolymer is preferably used in terms of impact strength.

[0004] Since the resin composition having improved impact resistance is excellent in exhibiting impact strength in a low-temperature atmosphere,
It is used as a pipe joint covering material in cold regions such as 0 ° C to -30 ° C.

As the graft copolymer to be mixed with the vinyl chloride resin composition, in order to improve the impact resistance, the components and composition of the rubber polymer in the graft copolymer, the particle size thereof, and the graft polymerization method are used. Conventionally, various improvements have been made. As a result, those having an average particle diameter of the rubber polymer in the graft copolymer of 150 to 200 nm have been widely used (JP-A-51-12854).

[0006]

However, when the above-mentioned graft copolymer is mixed with a vinyl chloride resin, there is a problem that the rigidity of the obtained resin composition is lowered and the surface hardness is softened. For this reason, when the obtained resin composition is molded and coated on a pipe joint, when the pipe is tightened with a tool such as a pipe wrench, the coating material on the pipe joint surface is torn off and peeled off. was there. Particularly, in a hot summer environment or a high-temperature environment such as a warm region, there has been a problem that the elastic modulus is reduced, the rigidity is lost, and it becomes extremely easy to peel off.

As described above, in a cold region in winter, the product has an impact strength that does not crack even if the product is dropped, and in a warm region in summer, the pipe joint coating material does not tear even when tightened with a pipe wrench or the like. There is no product that combines the two characteristics of product strength. Recently, it has enough impact resistance to withstand drops and impacts in cold regions, and rigidity enough to prevent the coated pipe joint surface from peeling in warm regions. It has become desirable to have a pipe joint coating having the following.

As a result of intensive studies on these problems, the present invention has found that by using a graft copolymer having a rubber polymer having a specific particle size, the impact strength in a cold region in winter and the impact strength in a warm region in summer can be improved. An object of the present invention is to provide a pipe joint covering material having product strength.

[0009]

According to the present invention, there is provided a graft obtained by graft copolymerizing a vinyl monomer with (1) a vinyl chloride resin and (2) a rubber polymer having an average particle diameter of 260 nm or more. A pipe joint coating material containing a copolymer, the coating material having an average particle diameter of 260 nm to 450 nm, and a rubber polymer being a butadiene-based polymer and / or a styrene-butadiene-based polymer. The pipe joint covering material, wherein the vinyl monomer is methyl methacrylate and / or styrene, and (1) a vinyl chloride resin and (2) an average particle diameter of 260 nm to 450 n.
A pipe joint coating material comprising a butadiene-based polymer and / or a styrene-butadiene-based polymer and a graft copolymer obtained by graft-copolymerizing methyl methacrylate and / or styrene. And a coating material comprising (1) a vinyl chloride resin and (2) a graft copolymer obtained by graft copolymerizing a vinyl monomer with a rubber polymer having an average particle diameter of 260 nm or more. It is a pipe joint covered with.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

As the vinyl chloride resin (1) used in the present invention, vinyl chloride or a mixture of vinyl chloride and a vinyl monomer copolymerizable therewith can be prepared by a suspension polymerization method, a bulk polymerization method, or a fine suspension method. Those copolymerized by a usual method such as a polymerization method or an emulsion polymerization method, an ethylene-vinyl acetate copolymer,
Examples thereof include graft copolymers of vinyl chloride with ethylene-ethyl acrylate copolymer or chlorinated polyethylene. Further, chlorinated vinyl chloride or vinylidene chloride may be used as a raw material of the vinyl chloride resin, but vinyl chloride is preferred because of its large effect.

The vinyl monomers copolymerizable with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate, and (meth) acrylic esters such as methyl (meth) acrylate and butyl (meth) acrylate. , Maleic esters such as butyl malate and ethyl malate, fumaric esters such as dibutyl fumarate and diethyl fumarate, vinyl ethers such as vinyl methyl ether, vinyl butyl ether and vinyl octyl ether, and vinyl cyanide such as acrylonitrile and methacrylonitrile. Α-olefins such as ethylene, propylene and styrene, vinylidene halides and vinyl halides other than vinyl chloride such as vinylidene chloride and vinyl bromide, and allyl phthalates such as diallyl phthalate And the like. These may be used alone or in combination of two or more. The use amount of these vinyl monomers is preferably not more than 20% by weight in the vinyl chloride resin.
It is more preferably at most 5% by weight.

The average degree of polymerization of these vinyl chloride resins is preferably from 400 to 850 as measured by JIS K6721. If it is less than 400, the impact resistance may be poor, and 85
If it exceeds 0, the melt viscosity at the time of processing becomes extremely high, and the processability may be deteriorated.

The graft copolymer (2) used in the present invention is obtained by graft copolymerizing a vinyl monomer to a rubber polymer having an average particle diameter of 260 nm or more, and has an effect of improving impact resistance. Having.

The average particle size of the rubber polymer is at least 260 nm, preferably from 260 to 450 nm, more preferably from 280 to 35 nm.
0 nm is more preferred. If it is less than 260 nm, the impact strength is reduced, and the resin composition becomes soft and the rigidity is poor, which is not preferable. Also, when the pipe joint is formed by coating on the surface of the pipe joint, when the pipe is fastened to the pipe joint with a pipe wrench or the like, the coating material on the surface of the pipe joint is torn off and peeled off, thereby reducing the workability with the pipe wrench. If it exceeds 450 nm, impact strength, moldability, cold shock resistance, and workability with a pipe wrench may be reduced.

The average particle size of the rubber polymer can be measured by dyeing the graft copolymer component by a conventional method using a transmission electron microscope and measuring the size of the dyed particles.

Examples of the rubber polymer include a butadiene polymer, a styrene-butadiene polymer and an acrylic polymer. Among them, butadiene-based polymers and / or styrene-butadiene-based polymers are preferable, and butadiene-based polymers are preferable in that the glass transition temperature of the rubber component is low and the impact strength in a low-temperature atmosphere is excellent. Is more preferred.

As the vinyl monomer to be graft-copolymerized with the rubber polymer, a vinyl monomer copolymerizable with the rubber polymer can be used. For example, an aromatic vinyl monomer such as styrene and a cyanide such as acrylonitrile can be used. Vinyl monomers, alkyl (meth) acrylates having an alkyl group having about 1 to 5 carbon atoms such as ethyl (meth) acrylate and butyl (meth) acrylate, and crosslinkable monomers such as divinylbenzene. However, the present invention is not limited to these. These may be used alone or in combination of two or more. Among them, methyl methacrylate and / or styrene are preferable in terms of great effect.

For example, in the case of a butadiene-based polymer, the graft copolymer obtained by graft copolymerizing a vinyl monomer with a rubber polymer is a mixture of butadiene and a vinyl monomer copolymerizable with butadiene. It is obtained by polymerization.

Examples of the graft copolymer used in the present invention include methyl methacrylate-butadiene-styrene copolymer, styrene-butadiene copolymer and methyl methacrylate-butadiene-acrylonitrile-styrene copolymer. No. Among these, a methyl methacrylate-butadiene-styrene-based copolymer is preferred because of its great effect.

There is no particular limitation on the method for producing a methyl methacrylate-butadiene-styrene copolymer by graft-polymerizing methyl methacrylate and styrene onto a rubber polymer such as a butadiene polymer. It may be carried out by a usual method, for example, a method such as emulsion polymerization, and a latex of a butadiene polymer is agglomerated or enlarged (increase the rubber diameter) with an acid to obtain a butadiene polymer having a specific particle size. Thereafter, it may be performed by a method of graft polymerization,
A method of adding a water-soluble electrolyte to agglomerate or enlarge latex particles of a butadiene-based polymer during graft polymerization may be used. The method of adding and copolymerizing a vinyl monomer during graft copolymerization is not particularly limited, and may be a multi-stage addition method or a batch addition method in which the monomer concentration at the time of dispensing is the same.

The amount of the graft copolymer to be added is preferably 5 to 30 parts by weight, more preferably 10 to 25 parts by weight, based on 100 parts by weight of the vinyl chloride resin. If the amount is less than 5 parts by weight, the impact strength is inferior, the cold shock resistance is reduced, and there is a possibility that cracks may be caused by dropping in a low temperature environment, and if it exceeds 30 parts by weight, the melt viscosity becomes too high and the moldability may be reduced. There is.

The pipe joint coating material of the present invention may contain, if necessary, stabilizers, processing aids, reinforcing agents, lubricants, fillers, pigments and the like used for general vinyl chloride resins.

Vinyl chloride resin and methyl methacrylate
In the pipe fitting covering material of the present invention containing a butadiene-styrene copolymer, a mixing order of a vinyl chloride resin or a methyl methacrylate-butadiene-styrene copolymer,
The mixing method and the pelletizing method are not limited, and generally, the mixing method and the pelletizing method are those used in the production of ordinary vinyl chloride resin. For example, a high-speed mixer such as a Henschel mixer or a super mixer, or a mixer such as a ribbon blender is used for mixing.

As a mixing method, it is preferable that the respective components are put into the above-mentioned mixer, mixed at a temperature of, for example, 150 ° C. or less for a time appropriate for each mixer, and uniformly blended.

The method for granulating the obtained pipe joint coating material is carried out using a machine such as a Banbury mixer, a mixing roll, and an extruder, which is used for producing a general vinyl chloride resin.

The pipe joint covering material of the present invention is obtained by injection molding using an injection molding machine.

There are no particular restrictions on the types of pipe joints that can be used in the present invention, such as those connecting straight pipes of the same diameter, such as sockets and couplings, and different diameters, such as sockets and reducers of reduced diameter. Connecting a straight pipe of
45 ° elbows, 90 ° elbows, 180 ° elbows, bents, etc., those that bend the direction of the pipe axis, T-shaped pipes, Y-shaped pipes, etc., with one branch, cross pipes and crosses And the like having two branches, and the shape and dimensions are determined according to the use and pressure resistance of the piping.

As a method for coating a pipe joint with a coating material,
Injection molding is preferred.

The material of the pipe joint of the present invention includes engineering plastic resin, metal and ceramic.
In particular, when a metal is used, it is advantageous in that it has high corrosion resistance.

[0031]

The present invention will be described below with reference to examples.

Experimental Example 1 Each raw material shown in Table 1 was put into a 75-liter Henschel mixer, mixed by stirring, and kneaded into pellets using a 90 m / m single screw extruder (manufactured by Ikegai Iron Works Co., Ltd.). 15 kg of resin composition pellets were obtained. The Izod impact strength of the obtained resin composition was measured. Table 1 shows the results.

(Materials used) Vinyl chloride resin: Commercial product, average degree of polymerization: 700 Graft copolymer: Methyl methacrylate-butadiene-styrene copolymer was used as the graft copolymer.
Methyl methacrylate-butadiene-styrene-based copolymer is a latex of butadiene-based polymer aggregated by acid,
A butadiene-based polymer having a specific particle size was obtained by enlargement, and a product obtained by graft-polymerizing methyl methacrylate and styrene by emulsion polymerization or the like was used.

(Measurement method) Particle size of rubber polymer: A sample was trimmed from a resin composition with a microtome, dyed with a 4% OsO ₄ solution at room temperature for 1 week, and sliced to a thickness of about 300 A (angstrom). The image was magnified 60,000 times with a transmission electron microscope, and a morphological image was taken. The obtained morphology photograph was digitized by an image scanner, taken into a computer, and the number and area of particles in a certain area were measured using image processing software to calculate the average particle diameter of the particles. Izod impact strength: according to JIS K7110.

[0035]

[Table 1]

Experimental Example 2 The resin composition of Experimental Example 1 was evaluated for moldability and cold shock resistance. Table 2 shows the results.

(Measurement Method) Formability: A metal pipe joint is mounted in a mold at a molding temperature of 200 ° C. using an injection molding machine having a mold clamping force of 200 t, and a coating material is coated on the surface of the pipe joint by injection molding. Coated. A 90 ° elbow (nominal diameter 50) specified by JIS K6739 was used as a pipe joint, and coating moldability was evaluated.場合 indicates that the pipe joint could be formed by coating, and X indicates that the pipe joint could not be formed by coating. Cold shock resistance: -3 per pipe joint formed in the moldability test
Under an atmosphere of 0 ° C., a 1 kg hard ball was dropped from a height of 1 m onto the pipe joint, and the presence or absence of cracks was evaluated. The case where there was no crack was evaluated as ○, and the case where there was crack was evaluated as ×.

[0038]

[Table 2]

Experimental Example 3 The resin composition of Experimental Example 1 was evaluated for pipe wrench workability. Table 3 shows the results.

(Measurement method) Pipe wrench workability: In a 60 ° C. atmosphere, the pipe joint covered by the formability test was assembled to an iron pipe using a pipe wrench, and the presence or absence of tearing on the pipe joint surface was evaluated. did. The case where there was no tear was indicated by ○, and the case where there was tear was indicated by ×.

[0041]

[Table 3]

Experimental Example 4 Izod impact strength was measured in the same manner as in Experimental Example 1 except that 15 kg of resin composition pellets shown in Table 4 were obtained using each raw material shown in Table 4. Table 4 shows the results
Shown in

[0043]

[Table 4]

Experimental Example 5 The resin composition of Experimental Example 4 was evaluated for moldability and cold shock resistance. Table 5 shows the results.

[0045]

[Table 5]

[0046]

According to the present invention, it is possible to obtain a pipe joint covering material having both impact strength in a low-temperature atmosphere and rigidity in a hot atmosphere.
It can be suitably coated as a pipe joint.

Claims (6)

[Claims] 1. A rubber composition comprising (1) a vinyl chloride resin and (2) a rubber polymer having an average particle diameter of 260 nm or more, and a graft copolymer obtained by graft copolymerizing a vinyl monomer. Become a pipe joint coating material. 2. The pipe joint coating material according to claim 1, wherein the average particle diameter is 260 nm to 450 nm. 3. The rubber polymer is a butadiene polymer and / or
The pipe joint coating material according to claim 1 or 2, which is a styrene-butadiene-based polymer. 4. The coating material for pipe joints according to claim 1, wherein the vinyl monomer is methyl methacrylate and / or styrene. 5. A graft copolymer of methyl methacrylate and / or styrene on (1) a vinyl chloride resin and (2) a butadiene polymer and / or a styrene-butadiene polymer having an average particle diameter of 260 nm to 450 nm. A pipe joint coating material containing a graft copolymer obtained by polymerization. 6. A rubber composition containing (1) a vinyl chloride resin and (2) a rubber polymer having an average particle diameter of 260 nm or more, and a graft copolymer obtained by graft copolymerizing a vinyl monomer. A pipe joint covered with a coating material.