JP2005179458A - Heat insulating material and its use method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a heat insulating material that has thermal storage performance in heat insulation time for many hours, is simultaneously safe even in excessive heating, is less liable to separate a solid matter of microcapsule from pigment to be heated by microwave irradiation. <P>SOLUTION: The heat insulating material comprises the solid matter of microcapsule enclosing a heat storage material and a pigment particle to generate heat by microwave irradiation at a ratio of particle diameter of the solid matter to the pigment particle of 0.2-5. The heat insulating material is safe by excessive heating and is less liable to separate water-absorbing pigment from the solid matter of microcapsule. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat insulating material that can heat and heat an object without continuously using energy from electricity or fuel. The heat-retaining material of the present invention relates to a heat-retaining material that retains a heat-retaining effect for a long time once it is heated by being irradiated with microwaves using a microwave oven and a method for producing the same.

  As a heat insulating material that is used without using energy of electricity or fuel, particularly as a heat insulating material for warming up in the cold, there are a warmer, a fire, a hot water bottle and the like. Recently, disposable chemical warmers using the oxidation reaction of iron powder have been accepted into the large market because of their simplicity and low cost, but there is a problem that they cannot be reused or finely regulated.

  A hot water bottle is generally used as a heat storage type heating tool. A hot water bottle is a heat storage type heat insulation material that uses the sensible heat of water (hot water). However, it is not easy to boil or fill hot water, there is a risk of burns, and the heat retention is inferior to the weight. Has drawbacks. Generally, as a means for extending the duration of the heat storage type heat insulating material, it is only necessary to increase the heat capacity of the heat insulating material. 1. Increase the amount of heat storage material (hot water in the case of hot water bottles). There are methods such as using a compound having a phase change instead of water, that is, a latent heat storage material.

  However, In this method, the weight of the heat insulating material is increased, and it takes time and a great deal of energy to boil hot water as a heat storage material as well as difficulty in carrying. On the other hand, 2. In order to realize this method, a compound having a melting point of at least 40 ° C., for example, a latent heat storage material such as an inorganic eutectic salt or paraffin wax, is put into a hot water bottle instead of hot water. Taking out at a temperature of 1 is complicated, and there is a lack of practicality such as a risk of ignition when heating.

  In order to solve the above-described problem, a heat insulating material has been proposed in which an appropriate temperature is maintained for a long time by heating a heat insulating material filled with an aqueous dispersion of microcapsules encapsulating a heat storage material (for example, a patent) Reference 1). Furthermore, this heat insulating material is characterized in that it can be easily heated by irradiation with microwaves emitted from a microwave oven or the like. However, as a problem in use, if microwaves are continuously irradiated excessively, the moisture of the contents gradually evaporates, and there is a risk that the packaging material may be damaged due to expansion.

  In order to solve the above-described problem, it has been proposed to fill a packaging material with a solid matter of a microcapsule that encloses a latent heat storage material and a pigment that can generate heat when irradiated with microwaves (for example, see Patent Document 2). By irradiating it with microwaves, heat can be stored easily and in a short time. That is: 1. Use of a heat insulating material obtained by filling a microcapsule solid and a pigment encapsulating a latent heat storage material, preferably in a breathable packaging material; The object is achieved by irradiating the heat insulating material with microwaves and heating it.

  The invention is achieved by mixing a microcapsule solid substance containing a latent heat storage material and a pigment capable of generating heat by microwave irradiation, and obtaining a powder having both in a single particle. . By heating this powder alone or in a suitable packaging material and irradiating with microwaves, heating and heat storage can be performed easily and in a short time. At this time, the effects of the invention can be achieved even if the microcapsule solid and the water-absorbing pigment are mixed separately.

However, if both are contained in a single particle, the microcapsule is damaged by excessive overheating, and there is a risk of ignition in some cases. On the other hand, when the pigment that can generate heat by the microwave irradiation and the microcapsule solid are separated as separate granulated materials, the difference in specific gravity is large, so that separation occurs in the course of use, and a sufficient effect cannot be obtained.
JP-A-8-19564 Japanese Patent Laid-Open No. 2001-288458

  In the present invention, there is provided a heat insulating material having a heat storage performance for a long time, and at the same time, it is safe even when excessive heating is applied, and a microcapsule solid and a pigment that can generate heat by microwave irradiation. An object is to provide a heat insulating material that hardly causes separation.

  As a result of investigations to solve the above problems, the ratio of the particle size of the microcapsule granulated material encapsulating the heat storage material to the pigment particles that can generate heat by microwave irradiation is 0.2 to 5 and is excessive. Thus, a heat insulating material that is safe even if the above heating is applied and that hardly separates the water-absorbing pigment and the microcapsule solid matter was obtained.

  The heat insulating material according to the present invention can be used as a solid heat storage material and, unlike a normal heat insulating material, can be kept warm for a long time after being heated once. Moreover, it is safe even if excessive heating is applied, and separation of the microcapsule solid and the pigment that can generate heat by microwave irradiation is difficult to occur.

  As a method for producing the microcapsules of the present invention, a physical method and a chemical method are known. In particular, as a method for microencapsulating a latent heat storage material, an encapsulation method by a composite emulsion method (Japanese Patent Laid-Open No. Sho 62-1452). Gazette), a method of spraying a thermoplastic resin on the surface of the heat storage material particles (Japanese Patent Laid-Open No. 62-45680), and a method of forming a thermoplastic resin in the liquid on the surface of the heat storage material particles (Japanese Patent Laid-Open No. 62-149334). Publication), a method of polymerizing and coating a monomer on the surface of heat storage material particles (Japanese Patent Laid-Open No. 62-225241), a method of producing a polyamide-coated microcapsule by interfacial polycondensation reaction (Japanese Patent Laid-Open No. 2-258052), and the like Method is used.

  As the membrane material of the microcapsule, polystyrene, polyacrylonitrile, polyamide, polyacrylamide, ethyl cellulose, polyurethane, aminoplast resin, or gelatin and carboxymethyl cellulose obtained by a technique such as an interfacial polymerization method, an in-situ method, or the like Synthetic or natural resin using coacervation method with gum arabic is used, but microcapsules using melamine formalin resin film and urea formalin resin film by physically and chemically stable in situ method are used. It is particularly preferred.

  The melting point of the heat storage material included in the microcapsule is preferably set in the range of about 20 to 80 ° C., and specific heat storage materials include waxes in the range of C16 to C40 and inorganic eutectics. And inorganic hydrates, fatty acids such as palmitic acid and stearin, and ester compounds such as behenyl behenate and stearyl stearate, preferably a compound having a heat of fusion of about 80 kJ / kg or more, chemically and physically Are stable and inexpensive. These may be used as a mixture, and a supercooling inhibitor, a specific gravity adjuster, a deterioration inhibitor and the like may be added as necessary.

  In general, the smaller the particle size of the microcapsule, the stronger the strength, and the weaker the larger the particle size, the weaker it is during the drying process or subsequent handling, and it is necessary to set an appropriate particle size. The range of 0.5 to 50 μm, more preferably 1 to 20 μm is preferable. The average particle system of the microcapsule indicates a volume average particle system measured using a particle size measuring device Multisizer II type manufactured by Coulter USA.

  Since the microcapsules of the present invention are usually obtained as an aqueous dispersion, dehydration, drying and granulation operations are required to obtain a solid. There are a centrifugal separation method, a filter press method, a screw press method, and the like as an apparatus for dehydrating or drying into powder, and a drying apparatus such as a drum dryer, a spray dryer, or a freeze dryer is used as a drying method. A spray dryer is a preferred method because it is easy to control the particle size without destroying the microcapsules. The average particle diameter of the powder obtained by these dehydration and drying apparatuses is set in the range of 5 to 300 μm, preferably 10 to 100 μm.

  These powders can be easily filled into the packaging material by increasing the average particle size through a granulation step, and the durability of the heat retaining effect is further improved. The granulation method differs depending on whether the sample is a powder or a wet product, but the top plate granulation method, wet extrusion granulation method, semi-dry extrusion granulation method, roll compression granulation method, tableting granulation Various granulation methods such as the method are used, but it is necessary to select an apparatus and conditions that do not damage the microcapsules. When granulating, a binder, a release agent, an antioxidant, a VOC adsorbent, activated carbon, a photocatalyst, various organic inorganic pigments, a non-combustible material, and a flame retardant can be kneaded or coexisted.

  The pigment particles used in the present invention are made of a material that can generate heat when irradiated with microwaves, and can be used as long as the molecular structure has polarity, and any inorganic or organic material can be used. As organic materials, polyamide resin, epoxy resin, melamine resin, polyester resin, acrylic resin, and those obtained by absorbing water in these materials can be used, and those having a relatively high heat softening point are in the form of beads or pellets. The processed form is used. As the inorganic material, mineral materials derived from natural products that are not flammable or explosive can be used, and water-absorbing pigments coordinated with water molecules are preferred materials. The water-absorbing pigment is a solid particle that absorbs moisture in the air relatively easily and in a large amount and can maintain a granular form without exhibiting deliquescence even after absorption. If the water absorption is low and the molecular structure is poor in polarity, it is not preferable because it does not rise to a sufficient temperature even if it is irradiated with microwaves, and if it is too high, it becomes sticky and the mixture tends to harden. Absent.

  As the pigment used in the present invention, inorganic salts, clay mineral pigments, natural minerals and the like are used. Preferably, highly water-absorbing pigments such as silica gel, activated alumina, magnesium silicate and zeolite are used, and these are single or Two or more types are used in combination.

  The particle diameters of the pigment particles and the microcapsule solids described in the present invention are arithmetic averages of the maximum diameter and the minimum diameter of the particles measured by an industrial caliper.

  The particle size ratio between the microcapsule solid and the pigment particles is preferably from 0.2 to 5, more preferably from 0.5 to 2. When used for a long period of time, whether larger or smaller than this, the microcapsule solids and the pigment particles are separated from each other, and the heat generated by the pigment particles is not stored in the microcapsule solids and the effect cannot be obtained.

  The shape of the pigment particles and the solid microcapsules may be any shape such as a sphere, an ellipse, a cube, a rectangular parallelepiped, a cylinder, a cone, a bowl, a regular polyhedron, a star, a cylinder, etc. A shape close to is desirable. The size is preferably molded into a granular form having a particle size of 0.1 to 20 mm. If it is smaller than 0.1 mm, it becomes difficult to handle because it powders, and if it is larger than 20 mm, the touch when touched becomes worse.

  There are no particular limitations on the type, size, and shape of the packing material that fills the solid microcapsules containing the pigment particles that can be heated by microwave irradiation and the heat storage material, but it can pass through the microwave well and repeatedly. It must be strong enough to withstand irradiation. In order to improve the feel, it is necessary to have some flexibility. Specific examples of the packaging material include synthetic or natural materials such as polyethylene, polypropylene, polyester, nylon, and natural rubber, in addition to natural fibers such as cotton, wool, and silk. The shape and size of the packaging material are not particularly limited, and are processed into a form suitable for the intended use. Since the surface of the packaging material gradually becomes hot due to microwave irradiation, covering the outside of the packaging material with a material that can insulate and retain heat to some extent, such as a cloth bag, improves the feeling of use and sustains heat generation. Time adjustment is also possible. The weight ratio between the microcapsule solid and the water-absorbing pigment is not particularly limited because the effect of the present invention is sufficiently exerted at any ratio.

  Microwaves are usually called high-frequency waves, and when a liquid having polarity is irradiated, the molecular motion becomes active and heating is possible. The most common irradiation device is a microwave oven, and a high frequency emitted from a magnetron is generally used. The heating method of the heat-retaining material according to the present invention is not limited to microwave irradiation, but heat can be similarly stored by heating until the heat-storing material is melted in hot water having a temperature equal to or higher than the melting point of the latent heat-storing material. A heating method using a microwave is preferable because the heat insulating material can be rapidly heated to a high temperature.

  Hereinafter, although the implementation procedure of this invention is concretely demonstrated as an Example, this invention is not limited to a following example. The particle size of the microcapsules was measured with a Coulter Counter (Coulter Electronics Co., UK, Coulter Multisizer), and the particle size of the pigment particles and the microcapsule solids was measured with an industrial caliper.

  80 g of paraffin wax having a melting point of 50 ° C. as a latent heat storage material was added to 100 g of an aqueous sodium salt solution of 5% styrene-maleic anhydride copolymer adjusted to pH 4.5 with vigorous stirring. The emulsion was emulsified until 3.5 μm. Next, 5 parts of melamine, 7.5 parts of 37% formaldehyde aqueous solution and 15 parts of water were mixed, adjusted to pH 8, and a melamine-formalin initial condensate aqueous solution was prepared at about 80 ° C. The whole amount was added to the above emulsion and the mixture was heated and stirred at 70 ° C. for 2 hours to carry out an encapsulation reaction. Then, the pH of this dispersion was adjusted to 9 to complete the encapsulation. The volume average particle diameter of the obtained microcapsules was 3.6 μm.

  This microcapsule dispersion was dried with a spray dryer to a moisture content of 3% or less to obtain a microcapsule powder. 30 parts by weight of 30% polyvinyl alcohol aqueous solution was added to 100 parts by weight of the obtained microcapsule powder, extruded by an extrusion granulator, and dried at 100 ° C. to obtain a microcapsule solid having a particle size of 2 mm. It was.

  80 parts by weight of silica gel particles having a particle diameter of 2 mm and 20 parts by weight of a solid capsule having a particle diameter of 2 mm were mixed, and 500 g was filled in a cloth bag. When heated for 2 minutes using a microwave oven, it was found that the warmth lasted for a long time, and even when used for a long time, the silica gel particles and the microcapsule solids did not separate in the packaging material. Maintained.

(Comparative Example 1)
30 parts by weight of 30% aqueous polyvinyl alcohol solution was added to the microcapsule powder obtained in the same manner as in Example 1, extruded by an extrusion granulator, dried at 100 ° C., and a microcapsule solid having a particle size of 30 mm. I got a thing.

  20 parts by weight of a solid capsule having a particle size of 30 mm and 80 parts by weight of silica gel particles having a particle size of 5 mm were mixed, and 500 g was filled in a cloth bag. When heated for 2 minutes using a microwave oven, it was found that the warmth persisted for a long time, but when used for a long time, the silica gel particles and the microcapsule solids were separated in the packaging material, and the heat retention time was short. became.

(Comparative Example 2)
20 parts by weight of microcapsule powder obtained in the same manner as in Example 1, 80 parts by weight of silica gel particles, and 30 parts by weight of 30% polyvinyl alcohol aqueous solution were mixed, and extrusion molding was performed using an extrusion granulator at 100 ° C. It was dried to obtain a solid material having a heat storage performance of 2 mm in particle size.

  When 500 g of the solid material having the above heat storage performance was filled in a cloth bag and heated for 3 minutes using a microwave oven, the solid material was burnt and a strange odor was generated.

  The heat insulating material according to the present invention can be used as a heat storage type heat insulating material such as a hot water bottle, and the heat retention time can be maintained for a long time. Moreover, it is not necessary to fill or unplug hot water each time it is used, and it can be used safely any number of times by simply irradiating it with microwaves. Furthermore, the touch always maintains softness. The thermal insulation material of the present invention is a thermal pad for medical use to relieve shoulder and lower back pain, gloves, socks, insoles of shoes and desiccant, muffler, clothes and other cold protection equipment, household, industrial and agricultural heat insulation. It can be applied to materials and building materials.

Claims (3)

The microcapsule solid material encapsulating the heat storage material and the pigment particles capable of generating heat by microwave irradiation are filled in the packaging material, and the particle size ratio of the microcapsule solid material and the pigment particle is 0.2 to 5 A heat insulating material characterized by that. The heat insulating material according to claim 1, wherein the particle size of the microcapsule solid is 0.1 to 20 mm. A method of heating and using the heat insulating material according to claim 1 by microwave irradiation.