JPH0556378B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention provides a resin composition, particularly a resin composition for pipes, which can be used in central heating using a hot water circulation method, and in particular in floor heating equipment. It has excellent durability and significantly suppresses the increase in dissolved oxygen in hot water due to the penetration of external oxygen, and prevents corrosion of metal parts such as heat exchangers and hot water circulation pumps.
The present invention relates to a resin composition for hot water circulation pipes that can significantly prevent the problem.

B. Prior Art Conventionally, pipes made of iron, copper, etc. have been mainly used as hot water pipes for floor heating. When the pipe is embedded in concrete during construction, it is often installed under the floor.
Once installed, subsequent repairs are often difficult, and typically require long-term durability, for example about 50 years. Because of these severe conditions, seamless pipes are easily obtained, so there is no possibility of leakage from joints, and they are cheaper, as is the case when using conventional pipes made of iron, copper, etc. Plastic pipes, which do not require construction costs due to welding operations and the like, and which do not corrode the pipe material itself, are starting to be used as they are more suitable. Polyethylene, polypropylene, polybutene, etc. are usually used, but when such plastic pipes are used in floor heating systems that use hot water circulation, it is surprising that significant corrosion is observed in metal parts such as heat exchangers and pumps. In fact, it has come to be recognized that this corrosion has not been recognized before when conventional iron and copper pipes were used, and there is a growing trend towards composite plastic pipes. However, the reality is that nothing has been found that completely satisfies the corrosion prevention requirements. For example, based on the assumption that the corrosion is caused by oxygen in the atmosphere penetrating and dissolving into hot water through the pipe material, increasing dissolved oxygen, we developed a composite polyethylene with an aluminum (Al) layer as an intermediate layer. Some attempts have been made to use pipes, but although the details are not clear, defects such as cracks in the Al layer have been observed, and the above requirements have not been met.

Further, conventional polyethylene and polypropylene have insufficient heat resistance, and other polyolefins are usually subjected to radiation crosslinking for the purpose of further improving heat resistance. In this case, since the degree of crosslinking is high and the crosslinking rate is selected to be high in order to increase productivity, harsh conditions are usually used, for example, irradiation with radiation (electron beam) with an intensity of 12 to 20 Mrad. Saponified ethylene-vinyl acetate copolymer (hereinafter sometimes referred to as EVOH) cannot withstand such intense irradiation;
Breakage and deterioration of the main chain are unavoidable, and even if an EVOH layer is used as an intermediate layer, the multilayer pipe cannot be crosslinked by radiation to produce a pipe with practically satisfactory oxygen barrier properties.

C Problems to be Solved by the Invention The present inventors have found that the gel fraction is low during blending and molding, and that this operation is possible, but that it does not cause deterioration of EVOH, which is one component of the blend. It is an object of the present invention to obtain a resin composition for a seamless pipe, particularly a hot water circulation pipe, and especially a floor heating pipe, which satisfies heat resistance and durability, and is free from corrosion.

D Means for Solving the Problems The present invention provides a resin composition comprising a saponified ethylene-vinyl acetate copolymer (A) having an ethylene content of 20 to 60 mol% and a saponification degree of 95% or more, and polybutene (B). , and a resin composition in which this composition is further blended with a modified polyolefin (C) modified with an unsaturated carboxylic acid or its anhydride in a modified amount of 0.01 to 10% by weight, especially for pipes, especially for hot water circulation pipes. It is a resin composition.

E. Effects of the Invention According to the present invention, as is clear from the Examples described later, even when hot water is circulated in a pipe obtained from the resin composition of the present invention, the rate of increase in dissolved oxygen in the hot water is very small. As a result, corrosion of metal parts such as heat exchangers due to the circulation of hot water can be minimized, and the pipes have excellent heat resistance and durability, so they can last for a long time. It can be used without any problems.

F. More detailed description of the invention Since the polybutene used in the present invention has excellent heat resistance and also has good blendability with EVOH, the excellent effects described above can be achieved by using polybutene. become. Here, polybutene refers to polybutene-1 homopolymers, vinyl monomers such as ethylene and propylene whose main component is polybutene-1, diolefin,
These include copolymers or graft polymers with carboxylic anhydride compounds, etc. In addition, other thermoplastic polymers such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, and thermoplastic elastomers such as ethylene propylene elastomer and polyisobutylene rubber may be blended with this polybutene within a range that does not impede the purpose of the present invention. Additionally, additives such as a lubricant, an antistatic agent, an ultraviolet absorber, an antioxidant, a crosslinking agent, a crosslinking aid, a metal tyrate agent, an inorganic powder, and a coloring agent can be added. Among these, maleic anhydride-modified polybutene is preferred.

In the present invention, it is effective to further blend a specific adhesive resin with EVOH and polybutene. By coexisting such a specific adhesive resin in a specific amount, a resin composition for pipes, particularly a resin composition for hot water circulation pipes, has physical properties that are more practically satisfactory.

As the adhesive resin used in the present invention, a modified polyolefin modified with an unsaturated carboxylic acid or its anhydride and having a chemically bonded modifier content of 0.01 to 10% by weight is preferably used. . The unsaturated carboxylic acid or its anhydride includes monobasic acids such as acrylic acid, methacrylic acid, and methyl methacrylic acid; dibasic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and hemicic acid; Examples include anhydrides, and at least one of these is used, with maleic anhydride being particularly preferred. The polyolefin used in the adhesive resin is α- having 2 to 12 carbon atoms.
Olefin polymers (polyethylene, polypropylene, etc.), linear low-density polyethylene which is a copolymer of ethylene and α-olefin having 3 to 12 carbon atoms, and copolymerization with α-olefin having 2 to 12 carbon atoms. Examples include copolymers with vinyl monomers {fatty acid vinyl esters (vinyl acetate, etc.), acrylic acid esters (ethyl acrylate, etc.), etc.}. Among these, maleic anhydride-modified polybutenes have higher heat resistance and are more preferably used. The degree of modification is defined as the content of the chemically bonded modifying agent.
0.01-10% by weight, more preferably 0.01-5% by weight
This is the area of

EVOH (A) used in the present invention has an ethylene content of 20
EVOH with ~60 mol% and saponification degree of 95% or more.
In areas where the ethylene content is less than 20 mol%,
The details of what seems to be related to the poor molding processability, which has excellent oxygen barrier properties, and the decrease in affinity with the olefin due to the decrease in ethylene content, are not clear, but the physical properties are sufficient to meet the purpose of the present invention. It cannot be a blend with specific characteristics. If the content exceeds 60 mol%, the oxygen barrier properties will gradually deteriorate, although the above-mentioned drawbacks will not occur, and the blend will not be able to enjoy the effects of the present invention, which is not preferable. The content is
More preferably, it is 25 to 55 mol%. Further, the degree of saponification must be 95% or more; if it is less than 95%, the oxygen barrier properties will be poor and the effects of the present invention cannot be enjoyed. Furthermore, two or more types with different ethylene contents selected from the range of 20 to 60 mol% ethylene content are used.
Blends of EVOH can also be used,
In this case as well, the effects of the present invention can be similarly enjoyed.

The EVOH of the present invention includes an olefin having 3 or more carbon atoms such as propylene, and a third component such as (meth)acrylic acid as a copolymerization component to the extent that oxygen barrier properties are not impaired, vinylmethoxysilane,
Silane modification obtained by copolymerizing vinyl silane such as vinyl ethoxysilane with ethylene and vinyl acetate, and saponifying the resulting copolymer.
Includes EVOH etc.

The blending amount of EVOH (A) is 10 to 50 parts by weight, preferably 15 to 45 parts by weight, per 100 parts by weight of polybutene (B). If the amount of EVOH(A) is less than 10 parts by weight,
The effect of suppressing oxygen permeation and increase in dissolved oxygen in hot water in the resulting pipe decreases, and if the amount exceeds 50 parts by weight, the physical properties decrease, making it difficult to be practically satisfactory.

In addition, the amount of polyolefin (C) modified with unsaturated carboxylic acid or its anhydride is higher than that of polybutene (B).
1 to 20 parts by weight, preferably 4 parts by weight per 100 parts by weight
~17 parts by weight. If the amount of (C) is less than 1 part by weight, the compatibility between polybutene (B) and EVOH (A) is insufficient, and depending on the extruder, the quality may fluctuate due to fluctuations in the extrusion amount and poor dispersibility. Easy to occur. Moreover, if it exceeds 20 parts by weight, the physical properties will deteriorate and it will be difficult to achieve a practically satisfactory result.

It is preferable to add and use an antioxidant in the resin composition of the present invention, but the effect of the antioxidant is relatively increased together with the effect of inhibiting oxygen penetration, so it is better than conventional products. The amount of antioxidant added may be smaller in order to achieve the same effect. As the antioxidant, for example, 3,5-t-butyl-
4-Hydroxytoluene, Irganox 1010,
Antioxidants known per se such as Irganox 1076 are preferably used.

The resin composition of the present invention can be used for molded articles, especially pipes,
It is especially useful as a resin composition for hot water circulation pipes, and the resulting pipe has the effect of significantly suppressing oxygen permeation, and also has a good resistance to bending during construction.
There is little risk of cracks etc. The outer diameter of the pipe is about 10 to 50 mm, and the pipe thickness is about 1 to 10 mm. The circulating hot water temperature is, for example, 60
-95°C, preferably 60-90°C.

As mentioned above, the resin composition of the present invention is particularly effective as a resin composition for pipes, especially hot water circulation pipes, but it can also be used for other sheets,
It can also be used as a resin composition for films and laminates. It can also be used as a resin composition for pipes for various liquids and gases, and for producing bottles by blow molding a parison.

The present invention will be further explained below with reference to Examples.
The present invention is not limited to these Examples.

Example 1 Density 0.952 for 100 parts by weight of polybutene-1
g/cc, melt index 0.5 g/10 min high-density polyethylene {Yukalon Hard BX manufactured by Mitsubishi Yuka
-50 (trade name)}, 5 parts by weight of modified polyethylene with a modification amount of 1.5% by weight modified with maleic anhydride, ethylene content 31 mol%, saponification degree 99.3%, melt index 1.2 g/10 minutes (190°C, 35 parts by weight of EVOH (2160 g load) was dry blended and fed into an extruder, and a pipe with a thickness of 2.1 mm and an outer diameter of 20 mm was obtained using a circular die at a die temperature of 210°C.

Water from which dissolved oxygen had been removed using a packed tower filled with metallic tin was circulated through the 50 m pipe, and the rate of increase in dissolved oxygen in the water was measured at the inlet and outlet of the pipe at a temperature of 70°C. The relative humidity in the atmosphere is 65
% (20℃), and the rate of increase in dissolved oxygen is
It was 104 μg/hr.

For comparison, a pipe with a thickness of 2.1 mm and an outer diameter of 20 mm was obtained using only the polybutene-1. Regarding this pipe, the rate of increase in dissolved oxygen was similarly measured. The rate was 3600 μg/hr.

Example 2 High-density polyethylene (melt index 0.1 g/10 minutes, density 0.955) as modified polyethylene
[Mitsubishi Yuka Yukalon Hard BX-70 (product name)]
except that 5 parts by weight of modified polyethylene modified with maleic anhydride with a modification amount of 1.5% and 35 parts by weight of EVOH with an ethylene content of 40 mol% and a saponification degree of 99.2% and a melt index of 3.5 g/10 minutes as EVOH were used. It was operated in the same manner as in Example 1. Example 1
The rate of increase in dissolved oxygen measured in the same manner as
It was 146 μg/hr.

For comparison, the thickness was 2.1 using only the polybutene.
A pipe with an outer diameter of 20 mm was obtained. The rate of increase in dissolved oxygen was 3800 μg/hr.

Example 3 To 100 parts by weight of polybutene-1 used in Example 1, 35 parts by weight of EVOH with 31 mol% ethylene and 99.3% saponification degree melt index 1.2 g/10 minutes (2160 g load at 190°C) was dried. The mixture was blended, melt-kneaded in a twin-screw extruder at 230°C, extruded into strands, cooled, and cut into pellets.

A pipe was obtained from this pellet by the method shown in Example 1. The rate of increase in dissolved oxygen measured in the same manner as in Example 1 was 110 μg/hr.

For comparison, a pipe molded product was obtained by directly dry blending polyolefin and EVOH using a twin-screw extruder without melt-kneading and cutting into pellets using a twin-screw extruder. The rate of increase in dissolved oxygen in the resulting pipe is 325
~105μg/hr, which varies greatly depending on the measuring pipe.
The quality was inconsistent.

Example 4 As modified polyethylene, high-density polyethylene (melt index 0.1 g/10 minute density 0.955) (Mitsubishi Yuka Yucalon Hard BX-70 (trade name)) was modified with maleic anhydride and the modification amount was 1.5% by weight. 5 parts by weight and 40 mol% ethylene content as EVOH, saponification degree 99.2 melt index
The same procedure as in Example 1 was carried out except that 45 parts by weight of EVOH at 3.5 g/10 minutes was used. The rate of increase in dissolved oxygen in the resulting pipe was 102 μg/hr.

Claims (1)

[Scope of Claims] 1. Consisting of a saponified ethylene-vinyl acetate copolymer (A) with an ethylene content of 20 to 60 mol% and a saponification degree of 95% or more and polybutene (B), and based on 100 parts by weight of (B) A resin composition containing 10 to 50 parts by weight of (A). 2. The resin composition according to claim 1, wherein (B) is maleic anhydride-modified polybutene. 3 Saponified ethylene-vinyl acetate copolymer (A) with an ethylene content of 20 to 60 mol% and a saponification degree of 95% or more,
Consists of polybutene (B) and a modified polyolefin (C) modified with an unsaturated carboxylic acid or its anhydride in a modified amount of 0.01 to 10% by weight, and (A) is 10 to 50 parts by weight per 100 parts by weight of (B). 1 to 20 parts by weight of (C). 4. The resin composition according to claim 3, wherein (C) is a modified polyolefin modified with maleic anhydride.