JP4734693B2 - Thermal storage - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a heat storage body using aliphatic polyester.
[0002]
[Prior art]
Plastic has good moldability, durability, and appearance, and is used in all fields of industry. However, few plastic materials generate heat by absorbing microwaves. For this reason, when manufacturing a simple heat storage body using a microwave oven, although using the latent heat at the time of the phase transition of the plastic solid-liquid layer, a separate microwave absorbent is added to absorb the microwave. As the absorbent, salts having crystal water are used.
[0003]
For this reason, there has been proposed an example (Japanese Patent Laid-Open No. 5-1282) etc. in which, after mixing paraffin or the like with polyethylene, sodium sulfate hydrate or the like is added and mixed, and then molded and used as a desired shape. However, it is complicated and the salt is not sufficiently dispersed, and there is a concern about problems such as leakage of low molecular weight components.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a simple plastic heat storage body that can be heated by a microwave such as a microwave oven using a plastic material that can be easily molded.
[0005]
[Means for solving problems]
As a result of intensive studies to solve the above problems, the present inventors have found an aliphatic polyester that absorbs microwaves such as a microwave oven, generates heat, and melts, and has led to the present invention.
[0006]
The aliphatic polyester resin used in the present invention is an aliphatic polyester resin composed mainly of a polycaprolactone resin, glycol and an aliphatic dibasic acid.
[0007]
The process for producing an aliphatic polyester resin comprising glycol and an aliphatic dibasic acid according to the present invention comprises the first step of polycondensing glycol and an aliphatic dibasic acid to form an aliphatic polyester oligomer, and if necessary, an aliphatic polyester. It consists of a second step in which an oligomer and a dicarbonate are reacted.
The first step of the present invention can be carried out by either a batch type or a flow type. Here, the batch type will be described.
[0008]
The first step is a step of polycondensation of glycol and aliphatic dibasic acid in the presence of a transesterification catalyst to remove water or alcohol by-produced during the reaction and excess glycol. The reaction is performed at a reaction temperature of 100 to 280 ° C. under reduced pressure. The pressure at which the above-mentioned purpose is achieved is selected as the pressure, and the pressure is preferably reduced to 300 mmHg or less for the purpose of promoting the reaction. In this step, different kinds of glycol, dicarboxylic acid compound and hydroxycarboxylic acid compound can be added and copolymerized.
[0009]
The molecular weight, acid value, and residual amount of dihydroxy compound of the aliphatic polyester oligomer can be controlled by appropriately balancing the distillation rate of unreacted dihydroxy compound and the reaction rate. Charge molar ratio, catalyst, temperature, reduced pressure A method of appropriately selecting and combining the conditions of the reaction time and the reaction time, and a method of blowing an inert gas at an appropriate flow rate are also realistic. Usually, it can be carried out by adjusting the degree of vacuum stepwise in the presence of a catalyst at a reaction temperature of 100 to 280 ° C. For example, esterification is first performed at normal pressure to remove water generated by the condensation reaction, then further dehydration condensation reaction is performed at a reduced pressure of about 200 to 80 mmHg to reduce the acid value, and finally to 5 mmHg or less. A method of making the degree of vacuum is used.
[0010]
By distilling off the excess dihydroxy compound and increasing the rate of increase in the degree of vacuum, the reaction time can be shortened and the residual amount of the dihydroxy compound in the oligomer can be reduced.
[0011]
In the second step, the aliphatic polyester oligomer obtained in the first step is reacted with a dicarbonate, the weight average molecular weight (Mw) by GPC in terms of styrene is at least 10,000, and the melting point is 50 to 180 ° C. This is a process for producing an aliphatic polyester carbonate. The reaction is usually carried out at 150 to 280 ° C., preferably 200 to 220 ° C., and the by-product hydroxy compound or water accompanying the reaction is removed. When the temperature is 150 ° C. or lower, a sufficient reaction rate cannot be obtained, and when the temperature is 280 ° C. or higher, the polymerization reaction can be accelerated, but the polymer may be colored, which is not preferable. In the reaction, it is preferable that the degree of vacuum is gradually adjusted as necessary, and the pressure is finally reduced to 3 mmHg or less.
[0012]
In order to facilitate pelletizing when a low molecular weight product is produced, a crystal nucleating agent can be added in the first step or the second step. Examples of the crystal nucleating agent include talc, mica, calcium carbonate, boron nitride and the like, and the addition amount is 0.001 to 1 part by weight with respect to 100 parts by weight of the raw material compound.
[0013]
The oligomer obtained in the first step can be used in applications where the molecular weight is low and the viscosity is required to be low when melted. If a certain level of viscosity is required at the time of melting, a method of increasing the viscosity as much as possible in the first step and increasing the molecular weight with a coupling agent or the like is also possible. However, in order to obtain a high molecular weight material with excellent thermal stability, it is desirable to proceed to the second step.
[0014]
The amount of dicarbonate added in the second step is determined by the oligomer molecular weight obtained in the first step, but the more the dicarbonate added, the lower the melting point of the resulting polymer. For this reason, the heat radiation temperature or melting temperature according to a use can be set with the addition amount of dicarbonate.
[0015]
The transesterification catalyst used in the first step and the second step is at least one selected from a Zr compound or an Hf compound and a Y, La, Zn, or Sn compound, and 5 × 10 ⁻⁵ to 100 parts by weight of the raw material compound. It is added in the range of 1 part by weight.
[0016]
The catalyst used in the present invention is selected from transesterification catalysts. In particular, a combination of a zirconium (Zr) compound or a hafnium (Hf) compound and one or more compounds selected from Y, La, Zn, and Sn. It is used in the range of 5 × 10 ⁻⁵ to 1 part by weight with respect to 100 parts by weight of the raw material mixture. Examples of preferable compounds as the catalyst include fatty acid salts, hydroxides, alcoholates, phenolates, acetylacetonates and the like.
[0017]
The glycol used in this step is an aliphatic glycol having a straight chain, branched or alicyclic structure having 2 to 20 carbon atoms, specifically, ethylene glycol, propanediol, butanediol, pentane. Examples include, but are not limited to, diol, hexanediol, octanediol, neopentyl glycol, cyclohexanedimethanol, tricyclodecadimethanol, and pentacyclodecadimethanol. Although selection is possible depending on the melting point of the material, etc., 1,4-butanediol is preferred in view of moldability and physical properties.
[0018]
As the aliphatic dibasic acid of the present invention, succinic acid is used as an essential component. Besides, for example, oxalic acid, malonic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanoic acid, azelaic acid, maleic acid Acid, fumaric acid and the like can be used in combination as appropriate. The above aliphatic dibasic acids may be esters or acid anhydrides thereof.
[0019]
Examples of the hydroxycarboxylic acid compound used in the present invention include lactic acid, glycolic acid, β-hydroxybutyric acid, hydroxypivalic acid, hydroxyvaleric acid and the like, and these can be used as derivatives such as esters and cyclic esters.
[0020]
These aliphatic dibasic acids, aliphatic dihydroxy compounds and hydroxycarboxylic acid compounds can be used alone or as a mixture and can be combined in any desired manner. However, in the present invention, they have moderate microwave absorption. However, those having a melting point high enough to realize practical heat resistance are preferred. Accordingly, in the present invention, it is preferable that 1,4-butanediol as the aliphatic dihydroxy compound and succinic acid as the aliphatic dibasic acid are contained in an amount of 50 mol% or more.
[0021]
In the present invention, a trifunctional or higher functional compound can be added as a branching agent in order to improve the shape stability during melting. As the branching agent, both an aliphatic compound and an aromatic compound can be used as long as the total amount of hydroxyl groups and carboxylic acid groups is trifunctional or more.
[0022]
Moreover, the aliphatic polyester carbonate obtained by making the aliphatic polyester obtained at the 2nd process and a carbonate compound react is also preferable.
Specific examples of carbonate compounds used in the production of aliphatic polyester carbonates include diaryl carbonates such as diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, and m-cresyl carbonate, and dimethyl carbonate and diethyl carbonate. And aliphatic carbonate compounds such as diisopropyl carbonate, dibutyl carbonate, diamyl carbonate, dioctyl carbonate, and the like, but are not limited thereto. Further, in addition to the above-mentioned carbonate compound composed of the same kind of hydroxy compound, an asymmetric carbonate compound and a cyclic carbonate compound composed of different kinds of hydroxy compounds can also be used.
[0023]
When the dicarbonate is added in the second step, block copolymerization is possible by adding a glycol component. The glycol to be added may be the same as or different from the glycol used in the first step.
[0024]
Such aliphatic polyesters of the present invention are those having a high molecular weight, such as injection molding, extrusion molding, inflation method, T-die method, spinning, filament molding, blow molding, vacuum pressure molding or foam molding. Can be formed. Add additives such as fillers, antioxidants, stabilizers, nucleating agents, UV absorbers, lubricants, waxes, colorants, colorants, contents, fillers, etc. that are usually added to polymers as needed can do.
[0025]
When a molded product is obtained using the aliphatic polyester of the present invention, the molecular weight of the polymer used is appropriately selected depending on the molding processing conditions, the type of the molded product, the molding temperature, etc., and the weight in terms of styrene measured by GPC Those having an average molecular weight Mw in the range of 10,000 to 300,000 are used.
[0026]
The melt viscosity of the aliphatic polyester is 500 to 30,000 poise. This melt viscosity is a melt viscosity measured by a flow tester under conditions of a temperature of 190 ° C. and a load of 60 kg.
[0027]
It is also possible to use it in the form of a composition containing the aliphatic polyester of the present invention. The content of the aliphatic polyester in the composition needs to be at least 5%, and below that, the effect of the present invention is small. As a method of containing, copolymerization or blending is possible, and it is also possible to contain an inorganic filler.
[0028]
In the case of copolymerization, there is no particular limitation as long as it is a method in which aliphatic polyester is copolymerized in a block state, and with aromatic and / or aliphatic polyester, aromatic and / or aliphatic polycarbonate, nylon, polyolefin, etc. Can be copolymerized.
When the material is blended, the resin to be mixed is not particularly limited, and can be blended with aromatic and / or aliphatic polyester, aromatic and / or aliphatic polycarbonate, nylon, polyolefin and the like.
[0029]
Next, a method for making the heat storage body of the present invention will be described. Here, a case where aliphatic polyester carbonate (a copolymer of 90% aliphatic polyester and 10% aliphatic polycarbonate) is used will be described.
[0030]
An aliphatic polyester carbonate is formed into a sheet-like or rod-like form and packaged with a non-microwave absorbent material or placed in a container to produce a heat storage body. The packaging material and container material are not particularly limited, but paper, cardboard, ceramics, ceramics, plastics, dry wood, cloth, etc. can be used. If the molten aliphatic polyester carbonate is worried about flowing out, it can be prevented by adding a lot of branching agent during the production of the heat storage body.
It can also be inserted in the form of a sheet in the lower part of a lunch box, dish, food tray or the like.
[0031]
Other heat accumulators can be used in the form of pellets. In this case, the strand can be manufactured and cut in a molten state with the material inside and the non-microwave absorbing polymer outside. It can be manufactured by coating a polymer material on pellets made of material.
[0032]
Further, the aliphatic polyester of the present invention can be used as a shielding material for microwaves emitted from a mobile phone or the like. In this case as well, the above-described form can be used, but it is necessary to consider the thickness in accordance with the amount of absorbed microwave in consideration of the temperature rise when a large amount of microwave is absorbed. If it is in a very small amount, it is not necessary to wrap it in particular, and it is possible to mold and use a housing of this material alone.
[0033]
The aliphatic polyester and polyester carbonate material comprising glycol and an aliphatic dibasic acid compound of the present invention has biodegradability by microorganisms, and by selecting other resins to be decomposed by microorganisms, microbial degradation can be achieved. It is also possible to obtain a molded article having a good property.
[0034]
As described above, according to the present invention, it is possible to produce a thermoplastic material that absorbs microwaves having sufficient formability and workability. In addition, the microwave absorbing material can be used for various processes such as multilayering, bonding, laminating, and bonding using microwaves, and can also be used as a heat storage body and a microwave shielding material.
[0035]
Next, the present invention will be described in more detail with reference to examples. Here, the case where aliphatic polyester carbonate using 1,4-butanediol as the glycol component, succinic acid as the aliphatic dibasic acid compound, and diphenyl carbonate as the dicarbonate is mainly exemplified.
[0036]
In this example, the molecular weight was measured as a weight average molecular weight (Mw) and a number average molecular weight (Mn) in terms of styrene by GPC (using GPC System-11 manufactured by Showa Denko KK) with chloroform as a solvent.
The residual amount of unsaturated bonds was measured using NMR (NMR EX-270 manufactured by JEOL Ltd.).
[0037]
The melt flow rate of aliphatic polyester or aliphatic polyester carbonate was measured using a melt indexer (Toyo Seiki) at a temperature of 190 ° C. and a load of 2.16 kg.
[0038]
The hydroxyl value and acid value of the aliphatic polyester oligomer were measured according to JIS K-1557. From the measured value of the hydroxyl value, the terminal hydroxyl group mole per unit weight was determined, and the half amount thereof was defined as the theoretical amount of the dicarbonate and / or dicarboxylic acid compound.
[0039]
Production Example 1
In a 50 liter reaction vessel equipped with a stirrer, a distillation condenser, a thermometer and a gas introduction tube, succinic acid 18,740 g (158.7 mol), 1,4-butanediol 21,430 g (237.8 mol) and Zirconium acetylacetonate (745 mg) and zinc acetate (1.40 g) were charged, and the mixture was reacted at a temperature of 150 to 220 ° C. for 2 hours under a nitrogen atmosphere to distill water. Subsequently, aging was carried out for 3 hours at a reduced pressure of 150 to 80 mmHg, and the dehydration reaction proceeded. Further, the reduced pressure was gradually increased so that the final reduced pressure was 2 mmHg or less, and water and 1,4-butanediol were further added. The reaction was stopped when the total distillate amounted to 10,460 g. The oligomer obtained had a number average molecular weight of 1,780, a terminal hydroxyl value of 102 KOH mg / g, and an acid value of 0.51 KOH mg / g.
[0040]
Next, 24,000 g of the obtained oligomer was charged into a 50-liter reaction vessel equipped with a stirrer, a distillation condenser, a thermometer, and a gas introduction tube, and 4,680 g of diphenyl carbonate was added. The reaction was finally performed at a temperature of 210 to 220 ° C. with a reduced pressure of 1 mmHg for 5 hours. The obtained high molecular weight product (A-1) had a melting point of 104 ° C., a weight average molecular weight (Mw) measured by GPC of 238,000, and MI of 2 g / 10 minutes. As a result of 13C NMR measurement, the polycarbonate component had 14.3% carbonate units.
[0041]
The obtained high molecular weight (A-1) pellets were dried by a vacuum dryer at a temperature of 90 ° C. for 5 hours, supplied to an extruder (screw diameter 20 mmφ, L / D = 25), and attached to the extruder. A sheet (B-1) having a thickness of 1 mm was produced by extrusion through a 200 mm T-die at a temperature of 185 ° C. B-1 was a white plate.
[0042]
Example 1
When the sheet (B-1) obtained in Production Example 1 was irradiated with microwaves in a 600w household microwave oven, the sheet was heated and melted after 5 minutes and became transparent, and the resin temperature reached 100 degrees. .
[0043]
Comparative Example 1
An attempt was made to heat a polycarbonate sheet having a thickness of 1 mm in a microwave oven in the same manner as in Example 1, but the temperature of the sheet only slightly increased after 5 minutes.
[0044]
Example 2
The sheet (B-1) obtained in Production Example 1 is put in a flat container made of polycarbonate with a height of 1 cm, a width of 5 cm, and a length of 10 cm without any gaps, and a lid is formed to create a heat storage material for keeping food warm. did. When microwave irradiation was performed for 15 minutes in a 600w home microwave oven, the temperature was easily raised and heat could be stored. When this was wrapped with a cloth and stored in a polystyrene foam container, it took 8 hours to return to room temperature.
[0045]
Comparative Example 2
The same operation as in Example 2 was carried out with a sheet made of polystyrene instead of the sheet (B-1), but a slight increase in temperature was observed even if microwaves were irradiated for 15 minutes in a 600w household microwave oven. Only observed.
[0046]
Example 3
A box was made from the sheet (B-1) produced in Production Example 1, and a beaker containing water was put in the box and the lid was placed. For comparison, a similar beaker with water was prepared, and both were heated simultaneously in a microwave oven. No increase in temperature was observed for those covered with the aliphatic polyester carbonate sheet, but an increase in temperature was observed for the naked one, and it was found that the microwave was shielded.
[0047]
[Effect of the present invention]
With the aliphatic polyester of the present invention, it is possible to provide a simple plastic heat storage material or microwave shielding material that can be heated in a microwave oven. Further, the obtained molded product has practically sufficient physical properties.

Claims (2)

A heat storage element that consists of aliphatic polyester carbonate and absorbs microwaves to generate heat and melt . The heat storage body according to claim 1, wherein the aliphatic polyester carbonate is obtained by reacting an aliphatic polyester with a carbonate compound.