JPH0439381A - Heat-storing material and low temperature-storing material - Google Patents

Abstract

PURPOSE:To obtain the title material capable of producing into free form, being small in volume change between ordinary temperature state and state when heat is stored or low temperature is stored and having high endurance and obtainable in simple process by impregnating a heat storing agent or low temperature storing agent into a silane crosslinked polyolefin. CONSTITUTION:The aimed material obtained by impregnating (B) (i) a heat storing agent consisting of wax, etc., or (ii) <=5C alkyl ester of wax, alpha-olefin or 12-20C higher fatty acid, fluid paraffin or mixture thereof into a silane- crosslinked polyolefin, normally having 10,000-1,000,000 (preferably 20,000-300,000) molecular weight at an amount of normally >=60vol.% (preferably about 65-75vol.%).

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to heat storage materials and cold storage materials.

[Conventional technology]

Heat storage materials and cold storage materials are being studied in each field from the perspective of energy conservation and sunshine utilization planning. Current main heat storage materials include those that utilize the sensible heat of liquids and solids, and those that utilize the latent heat of phase change between solids and liquids of inorganic and organic materials. In particular, devices that use latent heat have been actively researched in recent years because they require a smaller temperature difference for heat storage and can store significantly more heat per unit weight than those that use sensible heat. Sodium sulfate-based materials, chloride-based materials, etc. have generally been used as heat storage materials that utilize latent heat, but they have drawbacks such as the need to be sealed because they deteriorate when exposed to air. Limited scope. In addition, demands for heat storage materials are becoming more sophisticated, requiring durability, safety, and consideration for environmental issues. Japanese Patent Publication No. 62-277
No. 484 is a heat storage product in the form of microcapsules, which is easy to handle and does not require a sealed container, by immersing spherical or flat polyethylene pellets cross-linked by radiation or peroxide in a solution such as paraffin oil and allowing them to swell. Discloses pellets. [Problems to be Solved by the Invention] However, implementing the method of crosslinking polyethylene using radiation or peroxide requires a huge amount of equipment, which has the serious drawback of high equipment and production costs. be. Furthermore, with cross-linking methods that use radiation, it is difficult to cross-link to the inside, and if the radiation dose is increased to cross-link to the inside, the surface may deteriorate, or the surface cross-linking may progress too much, making it impossible to impregnate the heat storage agent or cold storage agent. There are problems that will go away. If the inside is not cross-linked, the inside will dissolve in the heat storage agent and will not be able to absorb the volume change due to the phase change of the heat storage agent, which may cause cracks to occur on the surface and the heat storage agent to flow out. In order to prevent this cracking, it is not only necessary to make the pieces into pellet-like or flat-shaped pieces, but also to design a filling container that takes volume changes into account, which limits its usage and is economically disadvantageous. Become. It is difficult to obtain a uniform product with sufficient strength and quality. In addition, in the crosslinking method using peroxide, it is necessary to heat and raise the temperature for crosslinking, and in general, the temperature has to be raised to above the melting point of the polyolefin, so the shape before crosslinking cannot be maintained and there is no freedom. It is difficult to manufacture such a shape. Moreover, as the degree of crystallinity decreases with melting, various properties also deteriorate. As a result of extensive research to solve the above-mentioned drawbacks, the present inventors have completed the heat storage material and cold storage material of the present invention, which are obtained by crosslinking polyolefin with silane and impregnating it with a heat storage agent or a cold storage agent. Ta. In other words, when the silane crosslinking method is used as a crosslinking method, it is possible to uniformly crosslink the entire surface at a temperature much lower than the melting point of the polyolefin, so it is possible to create a shape of any shape without causing surface deterioration, cracks, or volume changes. Heat storage materials can be manufactured. In addition, physical durability, thermal cycle durability, sealing performance, etc. are improved (and the equipment for crosslinking is greatly simplified, which is industrially advantageous. We also considered cold storage materials.Since cold storage agents have a lower melting point than heat storage agents, they usually have a smaller molecular weight and can easily dissolve polyolefins.For this reason, if the crosslinking of polyolefins is insufficient, it is difficult to impregnate the cold storage agent. Polyethylene that has been crosslinked with radiation or peroxide has been difficult to use as a cold storage material.However, silane crosslinking It was discovered that when polyolefin cross-linked to an appropriate extent is impregnated with a regenerator, it does not dissolve and exhibits sufficient performance, durability, heat cycle resistance, etc. as a regenerator material, leading to the completion of the present invention. Ta.

[Means for Solving the Problems] That is, the present invention relates to a heat storage material obtained by impregnating a silane-crosslinked polyolefin with a heat storage agent and a cold storage material obtained by impregnating a 7-run crosslinked polyolefin with a heat storage agent. The present invention will be explained in detail below. First, a method for producing the silane crosslinked polyolefin used in the present invention will be described. As the polyolefin used in the present invention, any polyolefin that can be crosslinked with silane can be used. Specifically, α-olefins having usually 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, are homopolymerized or copolymerized by known methods, such as polyethylene, polypropylene, polybutene, and ethylene/propylene copolymers. , ethylene/1-butene copolymers, and mixtures thereof. The molecular weight of the polyolefin is usually 10,000 to 1.
00o, ooo, preferably 20.000-300.
A value of about 000 is desirable. The silane-crosslinked polyolefin used in the present invention can be obtained by any known method. For example, a polyolefin is first reacted with a silane in the presence of a free radical generator and then the resulting product is contacted with water in the presence of a silanol condensation catalyst to obtain a silane-crosslinked polyolefin. The above silane has the general formula si RR' Y2 (
Here, R is an olefinically unsaturated monovalent hydrocarbon group or a hydrocarbonoxy group, Y is a hydrolyzable organic group, and Rl is R or Y. can. In the above general formula S IRR' Y2, examples of the group R include vinyl group, allyl group, butenyl group, cyclohexenyl group, cyclopentagel group, etc. 'There are a lot of people. Examples of the group Y include alkoxy groups such as methoxy, ethoxy, and butoxy groups, acyloxy groups such as formyloxy, acetoxy, and probionoxy groups, oxime groups, alkylamino groups, and arylamino groups. The most preferred examples of these silanes include vinyltrimethoxysilane and vinyltriethoxysilane. The proportion of the silane used can be arbitrarily changed depending on the reaction conditions or the degree of modification, but for boat fishing it is usually 0.1 to 50% by weight, preferably 0.5 to 10% by weight, based on the polyolefin to be modified. Weight%. As the free radical generator, peroxides and peresters are preferred. Specific examples of these include benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-di(peroxybenzoate)hexyne-3
, 1,3-bis(tert-butyl-peroxyisopropyl)benzene, perrllyl lauroyl, tert-butylperacetate), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne -3,2,5-dimethyl-2
, 5-di(tert-butylperoxy)hexane and tertiary
-butyl perbenzoate, azo compounds such as azobisisobutyronitrile and dimethyl azodiisobutyrate, dicumyl peroxide being most preferred. The amount of the free radical generator used is 0.05 to 0.5% by weight, preferably 0.05% by weight, based on the polyolefin to be modified.
Preferably, it is used in an amount of 1 to 0.2% by weight. To silane-modify a polyolefin, the polyolefin, silane, and a free radical generator may be reacted in any suitable apparatus. The reaction temperature is usually 100°C or higher, and can be carried out at any temperature lower than the decomposition temperature of the polyolefin, preferably at 120 to 250°C. The reaction time is usually within 10 minutes, preferably 2 to 5 minutes. Further, as the reaction device, any device can be used, such as an extruder, a Banbury mixer, a roll mill, or the like. A known method can be used to crosslink the silane-modified polyolefin thus obtained. That is, a silane-crosslinked polyolefin can be obtained by molding a silane-modified polyolefin by extrusion or other treatment and then bringing it into contact with water in the presence of a silanol condensation catalyst to cause a reaction. The shape of the silane-modified polyolefin is not limited in terms of the crosslinking reaction that will be carried out subsequently, so it is usually molded into the shape of the final product. Examples of silanol condensation catalysts include dibutyltin dilaurate, stannous acetate, stannous octoate (stannous caprylate), lead naphthenate, lead caprylate, iron 2-ethylhexanoate, and cobalt naphthenate. carboxylate,
metal compounds such as titanate esters and chelates such as titanate tetrabutyl ester, titanate tetranonyl ester and bis(acetylacetonitrile) di-isopropyl titanate, bases such as ethylamine, hexylamine, dibutylamine, and pyridine. , acids such as inorganic acids and fatty acids. Suitable catalysts are organic compounds such as dibutyltin dilaurate, dibutyltin diacetate and dibutyltin dioctoate. The silanol condensation catalyst is preferably mixed into the silane-modified polyolefin before contacting with water. That is, it can be achieved by mixing a silanol condensation catalyst during or after the reaction between silane and polyolefin. The amount of the silanol condensation catalyst added is usually 0.01 to 0.5% by weight, preferably 0.0% by weight based on the unmodified polyolefin.
It is 2 to 0.2% by weight. Although moisture present in the atmosphere is usually sufficient for reaction of the composition thus obtained with water to effect silane crosslinking, immersion in water or hot water or in a steam atmosphere may be used to increase the rate of crosslinking. This can be done by a method such as exposing. The degree of crosslinking can be appropriately selected depending on the purpose by adjusting the reaction conditions. In the present invention, the composition before contacting with water may contain other auxiliary agents, such as carbon black, talc, calcium carbonate, foaming agents, lubricants, antioxidants, ultraviolet stabilizers, heavy metal deterioration inhibitors, Various additives such as colorants and voltage stabilizers can be appropriately blended. A silane-crosslinked polyolefin is thus obtained, which is then impregnated with a heat storage agent or a cold storage agent. The heat storage agent that can be used in the present invention includes waxes such as hydrocarbon wax and oxygen-containing wax. Hydrocarbon waxes generally include petroleum distillate waxes, synthetic waxes, and natural waxes. The petroleum distillate wax referred to here specifically includes unrefined paraffin wax separated by a suitable dewaxing method from petroleum vacuum distillation distillate oil, vacuum distillation residue oil, heavy distillate oil, etc. Crystalline waxes such as slack wax and scale wax, as well as these unrefined petroleum distillate waxes, are treated with solvents, sweated,
Synthetic waxes include refined petroleum distillate waxes that have been decolorized and purified by acid/alkali washing, clay treatment, hydrogenation, etc.Specifically, synthetic waxes include those obtained by homopolymerization or copolymerization of olefins such as ethylene and propylene. Waxes, waxes obtained by thermally decomposing polymeric plastic-like or rubber-like polyolefins, polyolefin waxes such as waxes obtained as by-products when producing polymeric plastic-like polyolefins, and Fischer m-Tropsch wax. . As the heat storage agent component in the present invention, these various hydrocarbon waxes can be used alone or in combination of two or more kinds. Specific examples of oxygen-containing waxes include natural waxes such as carnauba wax, montan wax, rice bran wax, beeswax, and wood wax, as well as synthetic waxes such as oxidized micro, oxidized paraffin, and various reactions thereof. and polycarboxylic acid-modified waxes obtained by addition reaction of hydrocarbon wax with unsaturated polycarboxylic acids such as maleic acid, itaconic acid, citraconic acid, and methaconic acid or their anhydrides; Examples include mixtures. Among the waxes mentioned above, paraffin wax, microwax and the like are preferred. The heat storage agent used in the present invention can be selected from those having a melting point that matches the temperature used as the heat storage material, and may be used alone or in combination. Specifically, in the case of paraffin wax, for example, wax types are classified according to the melting point range according to the JIS standard, so it can be easily selected using this as a reference. When used as a normal heat storage material, the melting point range of the heat storage agent is preferably about IlO to IH'F, and 11
5 to +45"F is more preferable. In addition, the cold storage agent that can be used in the present invention includes, for example, the waxes mentioned above, as well as those having a carbon number of 12 to 20, such as α-olefin, myristic acid, and oleic acid. Examples include alkyl esters of 10,000-grade fatty acids having 5 or less carbon atoms, liquid paraffin, etc., and mixtures thereof, but liquid paraffin is preferable from the viewpoint of stability, processability, etc. In normal cases, when used as a cold storage agent, The melting point temperature range of the cold storage agent is −
The temperature is preferably about 20 to 10°C. In the present invention, a method for incorporating a heat storage agent or a cold storage agent into a silane-crosslinked polyolefin is generally to melt the heat storage agent or a cold storage agent by raising the temperature to a temperature above the melting point and below I80° F., and then immerse the silane-crosslinked polyolefin in the melted heat storage agent or cold storage agent. The impregnation rate of the heat storage agent or cold storage agent in the heat storage material or cold storage material can be determined depending on the use and shape, but it is usually 60 vol% or more, preferably about 65 to 75 vat%. When the heat storage material and cold storage material of the present invention obtained by the above-mentioned method are used by filling a container in the form of pellets, adhesion of porous powder such as clay to the surface of the pellets may prevent the pellets from adhering to each other. It is possible to prevent this from occurring and maintain the heat transfer surface area in its initial good condition. The powder can be attached by simply sprinkling the powder onto the surface of the pellet at room temperature, but it is preferable to do so at a temperature higher than the melting point of the heat storage agent or cold storage agent used, since this will result in better adhesion. [Examples] The present invention will be specifically explained below using Examples, but the present invention is not limited thereto.

[Example 1] A mixture obtained by adding 2.5 parts by weight of vinylmethoxysilane and 0.17 parts by weight of dicumyl peroxide to 100 parts by weight of polyethylene (molecular weight 100,000) was
The mixture was extruded into strands and pelletized using a 5 mm/llφ extruder at an extrusion temperature of 180° C. and a resin residence time of 100 seconds (screw rotation speed: 45 rpm). To 95 parts by weight of this pelletized material, a catalyst masterbatch, that is, 100 parts by weight of the polyethylene, 1 part by weight of dibutyltin dilaurate,
parts by weight and 4,4'-thiobis(B-t-butyl-
A mixture of 2 parts by weight of 4-hydroxybenzyl) and 5 parts by weight of a pelletized product of 4-hydroxybenzyl) were mixed, and the resulting mixture was
The mixture was pelletized again using a /i+φ extruder at an extrusion temperature of 230°C. This re-pelletized material was immersed in water at 90° C. for 6 hours to undergo crosslinking treatment to obtain pellet-shaped silane crosslinked polyethylene. Next, the silane-crosslinked polyethylene pellets were immersed in melted paraffin wax (130P standard product) having a melting point of 55° C. for 1 hour to impregnate the pellets with the paraffin as a heat storage agent. The content of heat storage agent in the heat storage material is 70
It was vo1%. Next, clay powder was attached to the surface of the pellet to form a heat storage material for filling. No outflow or bleeding of the heat storage agent was observed in the obtained heat storage material. Next, the obtained heat storage material is heated between 20°C and 70°C.
Although cooling was repeatedly performed, no cracks were generated or the heat storage agent leaked out, and an amount of latent heat corresponding to the calculated value was observed. Further, the volume change between 20° C. and 70° C. was 4% or less, which was a large amount of change absorbed compared to the 20% volume change associated with the phase change of paraffin alone.

[Example 2] The pelleted silane crosslinked polyethylene obtained in Example 1 was
Flow barf with melted pour point IO°C. (trade name: High White, manufactured by Nippon Gayu Co., Ltd.) for 1 hour, and the paraffin was impregnated into the pellet as a cold storage agent to obtain a cold storage material. The content of the cold storage agent in the cold storage material was 73 vol%. Next, clay powder was attached to the surface of the pellet to form a cold storage material for filling. The obtained cold storage material was repeatedly cooled and heated between -Iθ°C and 20°C, but no cracks were generated or the cold storage agent leaked out, and an amount of latent heat corresponding to the calculated value was observed.

[Comparative Example 1] The polyethylene used in Example 1 was molded into pellets,
Radiation crosslinking was performed, and the same paraffin as in Example 1 was impregnated as a heat storage agent in the same manner as in Example 1 to obtain a heat storage material. The content of the heat storage agent in the heat storage material was l1iOvo1%. Next, clay powder was attached to the surface of the pellets to prepare a heat storage material for filling. When the obtained heat storage material was repeatedly heated and allowed to cool between 20° C. and 70° C., it was observed that the amount of latent heat decreased from the initial value. Further, the volume change between 20°C and 70°C was about 8%.

[Comparative Example 2] A velarette-shaped molded product of polyethylene that was radiation-crosslinked in the same manner as in Comparative Example 1 was impregnated with the same regenerator as in Example 2 in the same manner and under the same conditions as in Example 2 to obtain a regenerator material. The content of the cold storage agent in the cold storage material was 70 vol%. Next, clay powder was attached to the surface of the pellet to form a cold storage material for filling. When the obtained cold storage material was repeatedly cooled and heated between IO°C and 10°C, it was observed that the amount of latent heat decreased from the initial value. Furthermore, the volume change between 20°C and 70°C was about 13%.

[Example 3] A mixture obtained by adding 2.5 parts by weight of vinylmethoxysilane and 0.17 parts by weight of dicumyl peroxide to 00i parts of polyethylene (molecular weight 80,000) was
The mixture was pelletized by extrusion into a strand using an extrusion temperature of 180° C. and a resin residence time of too seconds (screw rotation speed: 45 rpm) using an I/intestinal φ extruder. This pelletized product 95
Pellets of the catalyst masterbatch, a mixture of 100 parts by weight of the polyethylene, 1 part by weight of dibutyltin dilaurate and 2 parts by weight of 4,4'-thiobis(6-tert-butyl-4-hydroxybenzyl), based on parts by weight. 5 parts by weight of the compound were mixed, and the resulting mixture was 20 x 2
It was processed into a sheet having a thickness of 0 C11 and a thickness of 1 mw. This sheet was immersed in 90°C water for 6 hours to undergo crosslinking treatment,
A sheet-like silane-crosslinked polyethylene was obtained. Next, the sheet-shaped silane-crosslinked polyethylene was immersed in melted paraffin wax (130P standard product) having a melting point of 55° C. for 1 hour to impregnate the paraffin as a heat storage agent to obtain a sheet-shaped heat storage material. The content of heat storage agent in the heat storage material is 6
It was 0 vat%. No outflow or bleeding of the heat storage agent was observed in the obtained heat storage material. Next, the obtained heat storage material is heated between 20°C and 70°C.
Although cooling was repeatedly performed, no cracks were generated or the heat storage agent leaked out, and an amount of latent heat corresponding to the calculated value was observed. Further, the volume change between 20°C and 70°C was 4% or less.

[Example 4] Silane crosslinking was carried out in the same manner as in Example 1, except that 0.20 parts by weight of Verhexin 25B (manufactured by NOF Co., Ltd.) was used in place of dicumyl peroxide to polypropylene (molecular weight 80,000). Pellet-shaped silane-crosslinked polypropylene was obtained. Furthermore, the same heat storage agent as in Example 1 was impregnated in the same manner as in Example 1 to obtain a heat storage material. The content of heat storage agent in the heat storage material was 75%. The obtained heat storage material was repeatedly allowed to cool while being heated between 20° C. and 70° C., but no cracks were generated or the heat storage agent leaked out, and an amount of latent heat corresponding to the calculated value was observed.

[Example 5] An ethylene-propylene copolymer (molecular weight 70,000) with a propylene content of 5 mo1% was crosslinked with silane in the same manner as in Example 1 to obtain a pellet-shaped silane crosslinked copolymer. . Furthermore, the same heat storage agent as in Example 1 was impregnated in the same manner as in Example 1 to obtain a heat storage material. The content of the heat storage agent in the heat storage material was 68%. The obtained heat storage material was repeatedly allowed to cool while being heated between 20° C. and 70° C., but no cracks were generated or the heat storage agent leaked out, and 4 Mft corresponding to the calculated value was observed.

【Effect of the invention】

The heat storage material and the cold storage material of the present invention solve the conventional problems of variation in quality and being limited to pellet or spherical shapes, can be manufactured into any shape, and can be manufactured at room temperature and during heat storage. Due to its small volume change during cold storage and high durability, it can be used in unprecedented forms, and when used by filling it into a container, it is extremely easy to design the shape of the container. Became. Furthermore, it has become industrially advantageous because it can be manufactured by a simple process.

Claims (4)

[Claims] (1) A heat storage material obtained by impregnating a silane crosslinked polyolefin with a heat storage agent. (2) A cold storage material obtained by impregnating a silane-crosslinked polyolefin with a cold storage agent. (3) The heat storage material according to claim 1, wherein the heat storage agent is a wax. (4) Cold storage agent is wax, α-olefin, carbon number 1
3. The cold storage material according to claim 2, which is an alkyl ester having 5 or less carbon atoms of 2 to 20 higher fatty acids, liquid paraffin, or a mixture thereof.