JPH0481622B2 - - 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. The present invention relates to a resin composition for hot water circulation pipes that has excellent durability and can significantly suppress an increase in dissolved oxygen in hot water due to penetration of external oxygen, and can significantly prevent corrosion of metal parts such as heat exchangers and hot water circulation pumps.

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 moreover, long-term durability, for example about 50 years, is usually required. Because of these harsh conditions, seamless pipes are easily obtained, so there is no possibility of joint leakage, and they are also cheaper and require less welding operations than when using conventional pipes such as steel or copper. Plastic pipes are starting to be used as they are more suitable because they do not require construction costs due to construction costs, and the pipe material itself does not suffer from corrosion. 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 was completely unrecognized when iron and copper pipes were used in the past.
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 permeating and dissolving into hot water through the pipe material, increasing dissolved oxygen, a composite polyethylene pipe with an aluminum (Al) layer as an intermediate layer was developed. Although some attempts are being made, the details of what seems to be caused by temperature changes are not clear.
Defects such as cracks in the Al layer were observed, and the above requirements were not 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, severe 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. Also, in JP-A-55-9611 and JP-A-56-93542, water-crosslinked polyolefins are
Films, sheets, and tanks laminated with EVOH are described, but there are also descriptions of blends of EVOH and water-crosslinkable polyolefins, and blends of these with polyolefins modified with unsaturated carboxylic acids or their anhydrides. There is no mention of using these as resin compositions for pipes, especially for hot water circulation pipes, and there is no mention of using these as resin compositions for pipes, especially for hot water circulation pipes, and there is
Water-crosslinked polyolefin and EVOH for EVOH layer
Even if a laminate with a two-layer structure is used as a hot water circulation pipe, not only does it not have sufficient hot water resistance, but it also cannot be expected to have a significant suppressive effect on the increase in dissolved oxygen in hot water. It is not possible to prevent problems from occurring.

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. Furthermore, by using a cross-linked blend resin that can impart a specific degree of cross-linking to the polyolefin resin, which is another component of the blend, after molding and also satisfy the heat resistance and durability, there is no corrosion. Moreover, it is an object of the present invention to obtain a resin composition for a seamless pipe, especially a hot water circulation pipe, and especially a floor heating pipe, which has no problems in durability.

D Means for Solving the Problems The present invention consists 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 a water-crosslinkable polyolefin (B). A resin composition, and a resin in which this composition is further modified with an unsaturated carboxylic acid or its anhydride, and a modified polyolefin (C) in which the amount of the modifier chemically bonded is 0.01 to 10% by weight. Composition,
In particular, the resin composition is for pipes, particularly for hot water circulation pipes.

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 The water-crosslinkable polyolefin (B) used in the present invention is
A polyolefin copolymerized or grafted with a compound containing a silyl group having a hydrolyzable organic group, which can be crosslinked by the action of water in the presence of a silanol condensation catalyst, with a degree of crosslinking of 55% or more. . More specifically, for example, the general formula R-Si(-OR') ₃ {R is H ₂ C=CH- or R′ is CH ₃ −, C ₂ H ₅ − or CH ₃ −O−CH ₂ −
There is a silane-modified polyolefin modified with a vinyl silane represented by }, which represents CH ₂ -. It is also possible to use a blend of unmodified polyolefins, but even in this case the degree of crosslinking of the blend must be at least 55%. The degree of crosslinking
If it is not 55% or more, an olefin having 2 to 3 carbon atoms will be unsatisfactory in terms of heat resistance and durability required when using hot water of 60 to 95°C, for example. Further, if the degree of crosslinking is too high, the flexibility will decrease, which is undesirable, and the degree of crosslinking is preferably 90% or less, more preferably 85% or less.

The degree of crosslinking in the present invention is 8 in xylene below the boiling point.
This refers to the undissolved weight fraction (gel fraction) when timed extraction is performed. Immediately, EVOH is dissolved and removed before the treatment. It is more preferable that the degree of crosslinking is 65% from the viewpoint of improving heat resistance and creep resistance. Specific examples of the compound containing a silyl group having a hydrolyzable organic group include vinyltrimethoxysilane, vinylethoxysilane, vinyltriacetoxysilane, and vinyltris (β-methoxysilane). A method for obtaining such a water-crosslinkable polyolefin by copolymerization is disclosed in Japanese Patent Application Laid-open No. 1986-
Although it is disclosed in Japanese Patent No. 9611, the copolymerization of vinylsilane and ethylene is performed under a pressure of, for example, 500 to 4000 Kg/cm ² , preferably 1000 to 4000 Kg/cm 2 .
cm ² , in a tank or tube reactor, preferably in a tank reactor, in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent, at a temperature of 100 to 400 °C, preferably 150 to 250 °C. React simultaneously or in stages. In this case, a third monomer such as vinyl acetate, acrylic acid, methacrylic acid, and their esters may be copolymerized to the extent that heat resistance, creep resistance, and durability are not impaired.

Examples of methods for imparting water crosslinkability through grafting include the method disclosed in Japanese Patent Publication No. 1711/1983. For example, a compound containing a silyl group that can be hydrolyzed into polyolefin and a radical generator are fed to an extruder, and the temperature is preferably 180 to 240°C.
It is extruded at a cylinder temperature of 200-220°C. In this case, examples of suitable radical generators include organic peroxides such as dicumyl peroxide and benzoyl peroxide.

The silane compound content of the copolymerized or grafted polyolefin is 0.001 to 15% by weight, preferably 0.01 to 5% by weight, more preferably 0.1 to 2% by weight.
It is.

Examples of the silanol condensation catalyst include dibutyltin laurate, dibutyltin diacetate, dioctyltin diacetate, dioctyltin dilaurate, cuprous acetate, inorganic acids, fatty acids, and bases such as ethylamine and dibutylamine. This silanol condensation catalyst is preferably used by being blended in advance with the water-crosslinkable polyolefin as a masterbatch with an unmodified polyolefin.

The polyolefin imparted with water-crosslinking properties by grafting has, for example, a carbon number of 2 to 12
A homopolymer of α-olefin, a copolymer of α-olefin (including random and block copolymers), and a third component such as vinyl acetate or acrylic acid are used to meet the required characteristics for the floor heating pipe. There are copolymers etc. that are copolymerized with α-olefin within a range that does not cause any damage. Among these, high-density polyethylene with a high degree of polymerization and polybutene are more suitable when the heat resistance is to be further improved.

In the present invention, it is effective to further blend a specific adhesive resin with EVOH and water-crosslinkable polyolefin. 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.

The adhesive resin used in the present invention has a degree of modification by unsaturated carboxylic acid or its anhydride.
A modified polyolefin having a content of 0.01 to 10% by weight is preferably used. The unsaturated carboxylic acids or anhydrides thereof include 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; and anhydrides thereof. At least one of these is used, and maleic anhydride is particularly preferred. The polyolefin used in the adhesive resin has 2 to 2 carbon atoms.
Polymers of 12 α-olefins (polyethylene, polypropylene, polybutene, etc.), linear low-density polyethylene which is a copolymer of ethylene and α-olefins having 3 to 12 carbon atoms, α-olefins having 2 to 12 carbon atoms
Olefin and vinyl monomers that can be copolymerized with it {fatty acid vinyl esters (vinyl acetate, etc.), acrylic esters (ethyl acrylate, etc.), etc.}
Examples include copolymers with Among these, maleic anhydride-modified polybutenes have higher heat resistance and are more preferably used. The degree of modification by unsaturated carboxylic acid or its anhydride is preferably in the range of 0.01 to 10% by weight, more preferably 0.01 to 5% by weight.

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%,
Although the details of what seems to be related to the poor moldability and the decreased affinity with the olefin due to the decreased ethylene content, although the oxygen barrier properties are excellent, 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 25
More preferably, it is 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.
EVOH etc. are also included.

The amount of EVOH(A) is water-crosslinkable polyolefin.
(B) 10 to 50 parts by weight per 100 parts by weight, preferably
15 to 45 parts by weight. If the blending amount of EVOH(A) is less than 10 parts by weight, the oxygen permeation of the resulting pipe and the effect of suppressing the increase in dissolved oxygen in hot water will be reduced, and if it exceeds 50 parts by weight, the physical properties will deteriorate, making it practical for practical use. It is difficult to be completely satisfied.

The amount of the polyolefin (C) modified with an unsaturated carboxylic acid or anhydride is 5 to 20 parts by weight, preferably 5 to 17 parts by weight, based on 100 parts by weight of the water-crosslinkable polyolefin (B). If the blending amount of (C) is less than 5 parts by weight, the compatibility between polyolefin (B) and EVOH (A) is insufficient, and depending on the extruder, the quality may vary due to fluctuations in the extrusion amount and poor dispersibility. is likely to occur. If it exceeds 20 parts by weight, the physical properties will deteriorate,
This is unlikely to be practically satisfactory.

It is preferable to add and use an antioxidant in the resin composition of the present invention, but since the action and effect of the antioxidant is relatively increased together with the effect of suppressing oxygen penetration, it is equivalent to that of conventional products. The amount of antioxidant added may be small in order to exhibit the effect of. As the antioxidant, for example, 3,5-t-butyl-4
- Antioxidants known per se such as hydroxytoluene, Irganox 1010, and Irganox 1076 are preferably used.

When the resin composition of the present invention is molded into a molded article, such as a pipe, the water-crosslinkable polyolefin is uncrosslinked and has a low gel fraction so that there is no problem with the molding. Crosslinking is carried out with water. In this case, crosslinking methods include leaving the pipe in the atmosphere for a long time and reacting with moisture in the atmosphere, immersing the pipe in hot water or water, and applying steam to the pipe. In short, a method can be used in which the silane-modified polyolefin is brought into contact with water. The degree of crosslinking of the crosslinked silane-modified polyolefin thus obtained can be 55% or more, preferably 65% or more.

The resin composition of the present invention can be used for products, 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 0.952g/cc, melt index 0.5g/cc
After mixing 100 parts by weight of 10-minute high-density polyethylene [Mitsubishi Yuka Yucalon Hard BX-50 (trade name)], 2 parts by weight of vinyltrimethoxysilane dissolved in acetone, and 0.2 parts by weight of dicumyl peroxide, the mixture was Using an extruder with a diameter of 65 mm and a L/D of 24, the mixture was melted at 230°C, kneaded, and extruded into strands, which were then cooled and cut into pellets (gels) of modified polyethylene to which 1.5% by weight of vinylsilane was added. fraction 0%) was obtained.

Next, to 100 parts by weight of this pellet, 5 parts by weight of a mixture of 2 parts by weight of dibutyltin laurate and 3 parts by weight of BX-50 was blended.
5 parts by weight of modified polyethylene with a degree of modification of 1.5% by weight obtained by modifying the polyethylene with maleic anhydride, and EVOH35 with an ethylene content of 31 mol%, a saponification degree of 99.3%, and a melt index of 1.2 g/10 minutes (190°C, 2160 g load). The weight parts were dry blended and fed into an extruder, using a circular die to obtain a pipe with a thickness of 2.1 mm and an outer diameter of 20 mm at a die temperature of 210°C. Then, steam at 110° C. was blown into the obtained pipe, and the outer surface was also brought into contact with the steam to cause crosslinking. After the crosslinking, EVOH was applied at 60°C using a mixed solvent of n-propanol/water = 6/4 (weight ratio).
After extraction and dissolution, the uncrosslinked polyethylene and modified polyethylene were dissolved and removed with xylene at a temperature below the boiling point, and the undissolved content (gel content) was determined. The degree of crosslinking is 74
It was %. In order to obtain the above-mentioned pipe, 0.5% by weight of Irganox 1010 was blended into the blended resin.

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 sample having a thickness of 2.1 mm and an outer diameter of 20 mm was crosslinked with steam in the same manner as above using only the water-crosslinkable polyethylene. The degree of crosslinking was 75%. Regarding this pipe, the rate of increase in dissolved oxygen was similarly measured. The rate was 3600 μg/hr.

Example 2 In Example 1, high-density polyethylene (melt index 0.1 g/10 minutes,
Density 0.955) [Mitsubishi Yuka Yucalon Hard BX-70
(trade name)], and the same procedure as in Example 1 was carried out, except that EVOH with an ethylene content of 40 mol% and a saponification degree of 99.2% and a melt index of 3.5 g/10 min was used instead of EVOH. of the resulting pipe
The degree of crosslinking determined after EVOH removal was 75%.
The rate of increase in dissolved oxygen measured in the same manner as in Example 1 was 146 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 water-crosslinkable polyethylene and crosslinked with steam in the same manner. The degree of crosslinking was 74%. The rate of increase in dissolved oxygen was 3700 μg/hr.

Example 3 Ethylene, vinylmethoxysilane, and a small amount of propylene as a chain transfer agent were supplied to a stirred autoclave with an internal volume of 1.5 mm, and t- as a polymerization initiator was supplied.
Butylperoxyisobutyrate ^was added and ethylene
A vinylmethoxysilane copolymer was continuously obtained.
The supply amount of ethylene, vinyltrimethoxysilane, propylene and initiator is 43Kg/each.
hr, 95 g/hr, 450 g/hr, and 2 g/hr, and the ethylene conversion rate was 15%. The melt index (according to JISK6760) and vinyl silane content of the obtained copolymer were 1.0 g/10 min, respectively.
It was 0.7% by weight. Example 1 was carried out in the same manner as in Example 1, except that 1% by weight of dibutyltin dilaurate was blended with this copolymer and used as the water-crosslinkable polyethylene. The degree of crosslinking after water crosslinking was 72%.
The rate of increase in dissolved oxygen measured in the same manner as in Example 1 was 110 μg/hr.

Example 4 Copolymerization was carried out in the same manner as in Example 3, except that the amount of vinyltrimethoxysilane supplied was changed to 190 g/hr. The ethylene conversion rate was 15%, and the melt index and vinyl silane content of the obtained copolymer were 1.0 g/10, respectively.
minute, and 1.8% by weight.

In the same manner as in Example 3, a pipe made of a blend of Chinese polyethylene, EVOH, and maleic anhydride-modified polyethylene was obtained. The degree of crosslinking after water crosslinking was 79%. The rate of increase in dissolved oxygen measured in the same manner as in Example 3 was 102 μg/hr.

Example 5 Density 0.952g/cc, melt index 0.5g/cc
Instead of high-density polyethylene for 10 minutes, a maleic anhydride modified product of the high-density polyethylene (degree of modification: 0.5) was used.
The same procedure as in Example 1 was conducted except that the maleic anhydride-modified polyethylene with a degree of modification of 1.5% by weight used in Example 1 was not used.

The dissolved oxygen increase rate of the obtained pipe was measured in the same manner as in Example 1. The rate was 120 μg/hr.

Example 6 In Example 5, instead of the maleic anhydride modified product of high density polyethylene, maleic anhydride modified degree
Example 5 was carried out in the same manner as in Example 5, except that 1.8% by weight of polybutene-1 was used. However, 45 parts by weight of EVOH was used per 100 parts by weight of the maleic anhydride-modified polybutene-1.

The dissolved oxygen increase rate of the obtained pipe was measured in the same manner as in Example 1. The rate was 92 μg/hr.

Example 7 Example 6 except that a blend of 50 parts by weight of maleic anhydride-modified polybutene-1 and 50 parts by weight of unmodified polybutene-1 was used instead of maleic anhydride-modified polybutene-1. I did the same as step 6. The dissolved oxygen increase rate for the resulting pipe was 99 μg/hr.

Example 8 In place of the maleic anhydride-modified product of the high-density polyethylene that had been given water-crosslinking properties by vinyltrimethoxysilane modification in Example 5, the modified product 30
Example 7 except that 70 parts by weight of the water-crosslinkable high-density polyethylene used in Example 1 was used.
I went in the same way.

The rate of increase in dissolved oxygen in the obtained pipe was measured and a value of 102 μg/hr was obtained.

Example 9 5 parts by weight of a mixture of 2 parts by weight of butyltin laurate and 3 parts by weight of BX-50 was blended with 100 parts by weight of the modified polyethylene pellets to which 1.5% by weight of vinylsilane was added as used in Example 1. 31 mol% of ethylene per 100 parts by weight, degree of saponification 99.3%,
Melt index 1.2g/10 minutes (2160 at 190℃
Dry blend 35 parts by weight of EVOH (g load),
The mixture was melt-kneaded in a twin-screw extruder at 230°C, extruded into strands, cooled, and cut into pellets.

The pellets were formed into a pipe shape and water-crosslinked with steam using the method described in Example 1.
The degree of crosslinking of the modified polyolefin was 75%. The rate of increase in dissolved oxygen measured in the same manner as in Example 1 was 100 μg/hr.

For comparison, we skipped the pelletizing operations by melt-kneading and cutting in a twin-screw extruder, directly dry blended modified polyolefin and EVOH, obtained a pipe molded product in a single-screw extruder, and then water-crosslinked it with steam. , the rate of increase in dissolved oxygen measured in the same manner as in Example 1 is
It varied greatly depending on the measuring pipe, ranging from 325 to 105 μg/hr, and the quality was not constant.

Example 10 In Example 9, high-density polyethylene (melt index 0.1 g/10 minutes) was used instead of BX-50.
Density 0.955) (Mitsubishi Yuka Yucalon Hard BX-70 (trade name) was used, and instead of 35 parts by weight of EVOH, 40 mol% of ethylene, saponification degree of 99.2, melt index of 3.5 g/10 minutes, and 45 parts by weight of EVOH were used. The operation was carried out in the same manner as in Example 9, except for using EVOH. It was 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 a water-crosslinkable polyolefin (B), and (B)
A resin composition containing 10 to 50 parts by weight of (A) per 100 parts by weight. 2. The resin composition according to claim 1, wherein (B) is water-crosslinkable polyethylene. 3 Saponified ethylene-vinyl acetate copolymer (A) with an ethylene content of 20 to 60 mol% and a saponification degree of 95% or more,
consisting of a water-crosslinkable polyolefin (B) and a modified polyolefin (C) having a degree of modification with an unsaturated carboxylic acid or its anhydride of 0.01 to 10% by weight, and (B)
10 to 50 parts by weight of (A) and 5 to 20 parts by weight of (C) per 100 parts by weight
Resin composition containing parts by weight. 4. The resin composition according to claim 3, wherein (B) is water-crosslinkable polyethylene. 5. Claim 3 or 4, wherein (C) is a modified polyolefin modified with maleic anhydride.
The resin composition described in .