JPS6017419B2 - Method for manufacturing polyester elastomer foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a continuous sheet-like polyester elastomer foam having a high magnification and a uniform fine closed cell structure.

The field of plastic foams has shown significant progress in recent years,
Foams such as polystyrene, polyvinyl chloride, polyethylene, and polypropylene are widely used in building materials, packaging materials, etc. due to their flexibility, lightness, and heat insulation properties. However, these foams have problems in terms of mechanical strength, elastic recovery, cold resistance, heat resistance, etc. Foams such as rubber, polyurethane, and ethylene-vinyl acetate copolymers are also known as foams with relatively excellent elastic recovery properties. However, rubber, polyurethane, etc. have extremely poor aging resistance, and only open-celled cells can be obtained, and closed-celled ones are difficult to obtain, so they have poor mechanical properties such as thermal insulation properties, compressive strength, elastic modulus, and tear strength. It cannot be made with a high foam material that satisfies the above. On the other hand, ethylene-vinyl acetate copolymers can be made into highly foamed materials with relatively excellent compressive strength and tear strength, but are still insufficient in terms of elastic recovery (rebound elasticity). However, it has a defect in that it cannot withstand use at high temperatures, especially in terms of heat resistance. The performance characteristics of these conventional foams are determined by both the properties of the base polymer and the foam morphology (eg, uniformity, closed cell nature, etc.). On the other hand, polyester elastomer has excellent mechanical strength, elastic recovery, rebound resistance, cold to heat resistance,
It is known to have properties such as oil resistance and chemical resistance, and can be expected to be a useful foam base material.

The extrusion foaming method (Japanese Unexamined Patent Application Publication No. 49-97872) is known as a technique for making polyester elastomer into a foam, but in order to foam at the same time as melt extrusion, a special device is required for the molding die. Otherwise, it will not be possible to obtain a molded product with the desired shape and size, and it will be extremely difficult to produce a homogeneous closed-cell foam. Therefore, the general practice is to form a large foam block and cut it as appropriate for use, but with this method it is difficult to obtain uniform quality, much less a continuous sheet. No. As an improvement to this melt extrusion foaming method, a method has been proposed in which the foaming agent is not decomposed and foamed during extrusion molding, but is foamed once in the mold after molding (Kokai No. 58767/1983). However, it basically has the above-mentioned drawbacks, and has the fatal defect that it cannot be made into a highly foamed material with a homogeneous foam structure. Therefore, the present inventors conducted studies aimed at overcoming the above-mentioned conventional drawbacks and continuously and economically producing a high-performance polyester elastomer foam having a homogeneous, fine, closed-cell cell structure. The above purpose is effectively achieved by irradiating a sheet of block polyether ester with a specific structure containing a specific blowing agent with ionizing radiation to give it a chemically crosslinked structure, and then heating and foaming it. The present invention was achieved by discovering that this can be achieved.

That is, the present invention mixes azodicarbonamide with a block polyetherester having a melting point of 100 to 180 pm, which is mainly composed of butylene terephthalate units and poly(alkylene oxide) glycol units, and forms it into a sheet. Then, 0.2 to 50 Mrad is applied to this sheet-like material.
After irradiating with ionizing radiation to impart a crosslinked structure,
The present invention provides a method for producing a sheet-like polyester elastomer foam, which is characterized by foaming by heating to a temperature higher than the decomposition temperature of azodicarbonamide. According to the method of the present invention, since the block polyether ester is chemically crosslinked with ionizing radiation, it can be foamed with appropriate fluidity in the heating foaming process, and has a homogeneous and fine closed cell structure. A highly foamed material with

The block polyether ester used in the present invention is
The short chain polyester unit is the hard segment, and the long chain polyether ester unit is the soft segment.
It is a so-called thermoplastic elastomer that behaves like a normal thermoplastic polymer when melted, but when solidified, the short chain polyester hard segments crystallize to form a type of physical crosslinked structure and exhibit rubber elasticity. It is.

Here, in the short chain polyester unit, the main components of the dicarboxylic acid component and the diol component are terephthalic acid and monomer.
, 4-butanediol, and 50 mol% or more of it must be butylene terephthalate units, which results in excellent moldability, mechanical strength, rubber elasticity, heat resistance, etc. . Note that other dicarboxylic acids other than terephthalic acid can be used as a copolymerization component, and such copolymerization components include dicarboxylic acids having 2 to 20 carbon atoms such as azelaic acid, sebacic acid, adipic acid, and decanedicarboxylic acid. Examples include aliphatic dicarboxylic acids, aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, and naphthalene dicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and the amount that can be polymerized is up to 50 mol% of the total dicarboxylic brewing components. It is. Particularly preferably used copolymerized dicarboxylic acid component is isophthalic acid, where terephthalic acid/isophthalic acid = 9
0-50/10-50 (molar ratio), more preferably 80
When used in a ratio of 50/20 to 50 (molar ratio), suitable results are obtained as a crosslinked foam of polyester elastomer. The diol component is essentially 1,4-butanediol, but in a small amount of copolymerization other aliphatic diols such as ethylene glycol, propylene glycol, neobentyl glycol, 1,5-bentanediol, Alicyclic diols such as 1,6-hexanediol, decamethylene glycol and cyclohexanedimethanol may also be used. The long chain polyether ester unit in the block polyether ester has a molecular weight of 35
Dicarboxylic brewing component of 0 or less and number average molecular weight of 500 to 6
,000, and this dicarboxylic acid component is substantially the same as the dicarboxylic acid component of the short-chain polyester unit.

Poly(alkylene oxide) glycols that react with dicarboxylic acid components to form long-chain polyether ester soft segments include polyethylene glycol,
Poly(1,2- and 1,3-propylene oxide) glycol, poly(tetramethylene oxide) glycol, poly(hexamethylene oxide) glycol, block or random copolymers of ethylene oxide and propylene oxide, block or random copolymers of ethylene oxide and tetrahydrofuran Examples include random copolymers, and poly(tetramethylene oxide) glycol is preferred in terms of competitive heat resistance, water resistance, mechanical strength, elastic recovery, and ability to form effective crosslinking bonds by ionizing radiation. The number average molecular weight of poly(alkylene oxide) glycol is 500~
6000, more preferably 800-3000. The block copolyena ester produced using poly(IJ alkylene oxide) glycol having a molecular weight in this range forms a stable microphase separation region, exhibits good rubber elasticity, and makes the polymer flexible. If the molecular weight is too small, or conversely too large, the rubber elasticity will be impaired or the mechanical strength will be lowered, which is undesirable. Furthermore, depending on the case, a polyfunctional component such as trifunctional or higher functional polycarboxylic acid, polyol, polyoxycarboxylic acid, etc. may be added to the block polyether ester, and by adding such a polyfunctional component, the melt viscosity can be increased. It is also possible to make the production of crosslinked foams easier due to the rise.

The amount of the polyfunctional component that can be added is 0.05 to 3.0 mol% based on the dicarboxylic acid and diol forming the polymer. Things that can be used as polyfunctional components include:
trimellitic acid, trimesic acid, pyromellitic acid, 3,
3',4,4'-penzophenonetetracarboxylic acid, 1
, 2,3,4-butanetetracarboxylic acid and derivatives thereof such as esters and acid anhydrides, glycerin, bentaerythritol, and sorbitol. However, the contribution of this polyfunctional component to the crosslinking part of the "chemically crosslinked" foam, which is the gist of the present invention, is extremely small, and the actual method of introducing crosslinking is carried out by a different method as described later. There is a need. The block polyether ester used in the present invention is substantially composed of the above-described short chain polyester units and the longest chain polyether ester units, and is composed of short chain polyester units and long chain polyether ester units. occupies a weight ratio of 20 to 8 to 80 to 20.

A particularly preferred composition is that the short chain polyester unit is polybutylene terephthalate or polybutylene terephthalate/polybutylene isophthalate copolymer, and the poly(alkylene oxide) glycol of the last chain polyether ester unit is poly(tetramethylene oxide). It consists of glycol. The preferable range of these copolymer composition ratios varies depending on the use of the foam, but for applications that strongly require flexibility and high elastic recovery, the proportion of long mirror polyether ester units should be 35 to 8% by weight, especially 40 to 7% by weight. For applications that strongly require high mechanical strength, heat resistance, chemical resistance, etc., it is preferable that the polyether ester unit contains 20 to 5% by weight, especially 25 to 4% by weight of the last chain polyether ester unit. Preferably. The method for producing the block polyether ester comprising these components is arbitrary, but one example of a suitable polymerization method is to add dimethyl ester of dicarboxylic acid to an excess of about 1.2 to 2.0 molar amount relative to the acid. A heating reaction is carried out under normal pressure at a temperature of about 150 to 250 q○ with a low molecular weight glycol and poly(alkylene oxide) glycol at a temperature of about 150 to 250 q○ in the presence of a normal esterification catalyst to perform transesterification and distill off methanol. It can be produced by heating wheel condensation at 200 to 270° C. under reduced pressure under Hada Niksei.

The block polyether ester thus produced has a logarithmic viscosity of 0.5 or more, preferably 0.7 or more. Further, the block polyether ester used in the present invention has a melting point of about 100 to 18 pi○, particularly 120 to 16 pi
500, and in this melting point range, the mutual relationship between the decomposition temperature of the blowing agent, the extrusion degree of the polymer, and the decomposition temperature of the polymer is satisfied. It can be a highly foamed body with a closed cell structure.

In order to satisfy this melting point range, as described above, the short mirror polyester unit of the block polyether ester must be converted to butylene terephthalate/butylene isophthalate = 90
It is preferable to copolymerize at a ratio of /10 to 50/50, particularly 80/20 to 50/50. Note that the melting point in the present invention is the melting peak temperature when melting at a temperature increase rate of 1000/min using a DSC (differential calorimeter).

Further, the block polyether ester may be mixed with other polymeric substances in a proportion of 5% by weight or less of the total weight for the purpose of modification.

Such polymeric substances include polyethylene, ethylene-vinyl acetate copolymer, ethylene/propylene copolymer, ethylene-acrylic acid copolymer, polypropylene, chlorinated polyethylene, chlorinated polypropylene, polyvinyl chloride, polyester, polyamide, polyurethane. , styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, etc. In addition, various stabilizers such as heat stabilizers, antioxidants, hydrolysis stabilizers, and light stabilizers, colorants (pigments, dyes), and antistatic agents may be added to the block polyether ester as long as they do not interfere with cross-linking or foaming. , a conductive agent, a reinforcing agent, a reinforcing material, a filler, an adhesive, a plasticizer, and other organic or inorganic additives may be used in combination. The addition may also take place during the polymerization of the block polyether ester. Among the so-called thermally decomposable blowing agents, the azodicarbonamide to be mixed with the block polyether ester has a decomposition temperature (180 to 210°) that is within the ideal range in relation to the extrusion temperature and decomposition temperature of the polymer. It is possible to achieve a better cell structure and expansion ratio than when using other thermally decomposable blowing agents.

The amount of azodicarponamide used can be arbitrarily changed depending on the desired expansion ratio, but is usually selected from the range of 0.1 to 40% by weight based on the block polyether ester. For example, when the purpose is to use it as a so-called foam, the mixing amount is 5 to 4 cloud amount%, preferably 10 to 25%.
% by weight, and the mixing amount when making a foam with a low expansion ratio for the purpose of modifying the block polyether ester as an elastomer, that is, for the purpose of reducing weight, high elastic recovery, and improving resistance to permanent set, is 0. 1-10% by weight, preferably 0.5
A range of ˜5% by weight is selected. In some cases, other thermally decomposable blowing agents such as sodium bicarbonate, ammonium carbonate, azobisisobutyronitrile, azodicarboxylic acid metal salts, etc. may be used together with azodicarbonamide.
Dinitrosobentamethylenetetramine, hydrazodicarbonamide, p-toluenesulfonyl semicarbazide,
Organic blowing agents such as s-trihydrazinotriazine and pisbenzenesulfonylhydrazide can also be used in combination.
Further, in order to smoothly and efficiently carry out the crosslinking reaction caused by ionizing radiation described below, a crosslinking accelerator may be added to the flocked polyether ester as necessary.

Here, the crosslinking accelerator is a compound having two or more vinyl type double bonds in the molecule, and typical examples thereof include divinylbenzene, diallylbenzene, divinylnaphthalene, divinylbiphenyl, divinylcarbazole, divinylpyridine, and These nuclear substitution homologs and near-green homologues,
Polyacrylates and polymethacrylates of aromatic polyhydric alcohols such as ethylene glycol dimethacrylate and hydroquinone dimethacrylate, divinyl phthalate,
Polyvinyl esters of aliphatic and aromatic polycarboxylic acids such as diallyl phthalate, diallyl maleate, bisacryloyloxyethyl terephthalate, polyallyl esters, polyacryloyloxyalkyl esters, polymethacryloyloxyalkyl esters, diethylene glycol divinyl able, hydroquinone PolyJ vinyl ethers and polyallyl ethers of aliphatic and aromatic polyhydric alcohols such as divinyl ether and bisphenol A diallyl ether, triallyl cyanurate,
Examples include triallyl phosphate and trisacryloxyethyl phosphate. Furthermore, the aliphatic and aromatic polyhydric alcohols constituting the crosslinking accelerator include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, trimethylolpropane, bentaerythritol, 1,4-butanediol, poly(tetramethylene oxide) glycol, 1,6-hexanediol, neobentyl glycol, hydroquinone, resorcinol, biphenol, p,p'-dioxybenzophenone, p,p'-dioxyphenyl ether, 1,4-dioxy Naphthalene and its close analogues are included, and polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, sebacic acid, adipic acid, itaconic acid, butenetricarponic acid, maleic acid, trimellitic acid, pyromellitic acid, and trimesine. acids and their near-green congeners. The amount of these crosslinking accelerators added is 0.1 to 30% by weight, preferably 0.3 to 30% by weight, based on the block polyether ester.
It is used in a range of 10% by weight. Some of these crosslinking accelerators have a plasticizing effect during hot molding. Further, a compound that aids or accelerates crosslinking may be incorporated into the block polyether ester by a method such as copolymerization or chemical modification.

Typical examples of these compounds include dicarboxylic acids or diols containing unsaturated groups, isocyanate compounds, and epoxy compounds. For example, dicarboxylic acids or diols containing an unsaturated group in the molecule are 31 (or 4
-) cyclohexene-1,2-dicarboxylic acid, 2-cyclohexene-1,4-dicarboxylic acid, 3-butene-1,
2-dicarboxylic acid, allyloxybenzoic acid, 31 (or 41) cyclohexene-1,2-dimethanol, 1-
(or 2-)cyclohexene-1,4-dimethanol,
Examples include 4-allyloxyphenol and related substances thereof, more preferably 0.01 to 10 mol%, more preferably 0.5 to 10 mol%.
It can be copolymerized and used in a range of 5 mol%. Isocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, hexamethylene diisocyanate, m- or p- Diisocyanates such as xylylene diisocyanate, and dimers thereof, 3
Contains multimers such as oligomers. These polyisocyanate compounds may be used in the form of derivatives reacted with polyester prepolymers, polyalkylene oxides, glycols, and the like. Epoxy compounds have one or two epoxy groups in the molecule, such as phenyl glycidyl ether, allyl glycidyl ether, 8,y-
Epoxypropyl ether, 1,4-bis(8,y-epoxypropoxy)butane, 1,6-bis(epoxyethyl)hexane, 2,2-bis[p-(8,y-epoxypropoxy)phenyl]propane, 1 -Epoxyethyl-3,4-epoxycyclohexane, 1-(8,y-
epoxypropoxy)-2-benzyloxyethane, 1
Examples include 1(B,y-epoxypropoxy)2-ethoxyethane, 1,4-bis(3,y-epoxypropoxy)benzene, and particularly preferred are epoxy compounds having the following structure. (However, n is an integer)
The flock polyether ester, azodicarbonamide and crosslinking accelerator can be mixed by conventionally known mixing methods.

Examples include mixing using a Banbury mixer, mixing roll, kneading extruder, Henschel mixer, etc., and immersing the block polyether ester in a solution containing a blowing agent and a crosslinking accelerator. In particular, in order to achieve uniform mixing with additives such as blowing agents, it is preferable to use the block polyether ester in powdered form and melt-kneaded. Melt kneading is usually performed at a temperature higher than the polymer flow start temperature and lower than the blowing agent's thermal decomposition temperature, more preferably (polymer flow start temperature +10°C) or higher (foaming agent thermal decomposition temperature -10°C).
This will be done below. The mixture is kneaded under the above mixing temperature conditions, and then simultaneously or subsequently formed into a sheet by extrusion molding.

In the present invention, the unfoamed sheet of the block polyether ester composition containing the blowing agent thus obtained is cross-linked by irradiating it with ionizing radiation.

Ionizing radiation is a general term for radiation that has the ability to ionize, such as X-rays, Y-rays, electron beams, and proton beams, and one or more of these radiations may be irradiated at the same time if necessary. . Among these, the effect when using an electron beam is excellent. Irradiation with ionizing radiation is sufficient to retain the gas generated from the blowing agent when the polymer composition is heated above its softening temperature, but not to the extent that it prevents substantial deformation of the polymer composition. , that is, 0.2 to 5 wind position ad,
More preferably, irradiation is performed at 2 to 3 mrad. Irradiation is 0.
If the d is less than 2M, a uniform fine closed cell structure cannot be obtained.
If it exceeds 50 Mrad, the fluidity of the polymer decreases and a high expansion ratio cannot be achieved, which is not preferable. Irradiation is usually carried out at room temperature, but irradiation may be carried out under heating.
However, the heating should be kept at a temperature lower than the thermal decomposition temperature of the blowing agent. It is essential that the block polyether ester foam of the present invention be chemically crosslinked.
That is, when the unfoamed or foamed sample obtained by the method of the present invention was placed in a 1-mesh wire mesh bag and soaked in tetralin at 120:00 for 3 hours, the percentage by weight of the unfallen portion was
When expressed as a gel fraction, the foam of the present invention needs to have a gel fraction of at least 5%, and preferably the block polyether resin has a gel fraction of 10 to 80%. Determine the dose of ionizing radiation to the sheet of Stell. The foamable block polyether ester sheet obtained as described above is heated to a temperature higher than the decomposition temperature of azodicarbonamide by an appropriate method to foam it. Examples of the heating foaming method include heating with a hot plate heating roller; Air or steam heating, heating in liquid, high frequency heating, or heating
Conventionally known methods such as an infrared heating method can be used, but a method in which the sheet is brought into contact with a heating layer such as a salt bath or a silicone layer and heated by infrared rays from above facilitates the production of a homogeneous open foam. It's an excellent method.

Since the resulting foam of the present invention is based on cross-linked flocked polyether ester, this is completely unexpected in a block polyether ester foam that does not have a substantially cross-linked structure. foaming ratio of 5 times or more,
In particular, it can achieve a high magnification of more than 1 sound, and contains uniform fine closed-cell foam, and has excellent elastic recovery properties, compressive elastic modulus, breaking strength, cold resistance to heat resistance, aging resistance, and resistance. It is possible to create foams that have both solvent properties. In addition, since it can be easily obtained as a continuous sheet, it can be used as a high-performance foam that is not found in conventional olefin-based, rubber-based, urethane-based foams, etc. for wall materials, roofing, flooring, houses, automobiles, ships, etc. It is useful as building materials, interior materials, and packaging materials. Also, it is possible to control the foaming ratio by changing the amount of foaming agent added, so of course it is 1.2 to 4.
It can also be made into a foam with a low expansion ratio of about twice that of the block polyetherester elastomer.For example, it can be used for packing, gaskets, gaskets, mechanical parts such as hinges, precision parts, and covering electric wires and cables. In applications such as the above, it is imparted with lightness and flexibility, and because it has a crosslinked structure, it can be greatly improved in performance such as heat resistance, chemical resistance, and longitudinal permanent deformation resistance. Note that these molded bodies can be applied by punching a sheet-like foam, wrapping, or the like. As described above, the method of the present invention is as follows. The present invention provides a method for easily obtaining a highly elastic, wireless continuous sheet-like foam having closed microcells from rock polyester ester elastomer under normal pressure, and its industrial significance is extremely large. It is.

The present invention will be specifically explained below using Examples.

In the main text of the specification and in the examples, "parts" or "%" are by weight unless otherwise specified. Further, in the present invention, the logarithmic viscosity is measured in orthochlorophenol under measurement conditions of 0.5% and 25 oo. Example 1 Dimethyl terephthalate 70. Base shoe, dimethyl isophthalate 30.0 parts, 1,4-butanediol 68. Akebono and 10 parts of poly(tetramethylene oxide) glycol (number average molecular weight approximately 1,000) were placed together with 0.05 part of titanium tetrabutoxide in a polymerization reaction vessel equipped with a stainless steel helical ribbon type Nada Azusa wing, and the mixture was heated at 17,000 for 30 minutes. ,
The methanol produced by heating at 22,000 for 9 minutes was removed from the reaction system.

The reaction temperature was then raised to 245q0, the pressure of the system was gradually reduced to 0.2 willow Hg, and the polymerization reaction was continued at this pressure for an additional 150 minutes, yielding a very sticky melt.
The logarithmic viscosity of the resulting flocked polyether ester measured in orthochlorophenol at 2500, 0.5% concentration was 1.30, and the melting point determined by DCC was 146.
It was qo. In addition, nozzle 1. 0 x L/D = 1.03 C/min temperature increase 1
00k9/The flow start temperature under a suspended load was determined 1
It is a polymer that has fluidity at 37°C. The block polyether ester thus obtained was made into a powder with an average particle size of 150 mm in liquid nitrogen, and 10 parts of this powder was mixed with 20 parts of azodicarbonamide and 2 parts of divinylbenzene.
The mixture was mixed in a Henschel mixer, then fed into a bag extruder whose cylinder was heated to a temperature of 150 to 160 qo, and extruded into a long sheet with a thickness of 3 ribs from a T-die with a width of 120 sails. .

Liu Xin ad is added to this sheet on both sides using a Van de Graff accelerator.
was irradiated with an electron beam.

Next, an infrared heater was installed above the bath, and loafs for feeding and taking were continuously fed onto a molten salt bath before and after the bath to heat and foam. A foam sheet was obtained. The temperature of the molten salt at this time was 220°C. The resulting foam with closed cells has a width of 200 cells, a thickness of 5.6, and an apparent specific gravity of 0.042.
, the average bubble diameter was 0.25 willow. The apparent specific gravity is determined by the following method, and the same applies to the following examples.
Baron's shoe polish Quantity Apparent specific gravity = volume of water at room temperature removed by the foam, and the bridging (gel fraction) of this foam was 32%.

Example 2 Dimethyl terephthalate 60. parts, 40.0 parts of dimethyl isophthalate, 68.0 parts of 1,4-butanediol. In the same manner as in Example 1, using 10 parts of poly(tetramethylene oxide) glycol and 10 parts of poly(tetramethylene oxide) glycol as starting materials, the log viscosity was 1.
28 Melting point 127℃, flow start temperature in flow tester 1
I got a block polyether ester song of 28o0.

100 parts of flocked polyether ester legs were mixed with 1 $ part of azodicarbonamide, 2 parts of divinylbenzene, and 0.3 parts of a heat stabilizer, and a foam was prepared in exactly the same manner as in Example 1.

Each step was carried out smoothly, and a continuous sheet of foam having closed cells similar to that of Example 1 was obtained. This foam sheet has a width of 18 m, a thickness of 4.6 cm, and an apparent specific gravity of 0.08.
3 average air bubbles were 0.28 skin.

Comparative Example 1 In Example 1, when the sheet was heated and foamed on a heating ramp without irradiating it with an electron beam, the sheet deformed and almost no vaporized gas was captured by the sheet, and the temperature and time were changed. However, it was not possible to obtain a foam sheet having uniform microcells.

In this comparative example, the sheet was completely dissolved in tetralin at 120 pm under all conditions and was not crosslinked.

Comparative Example 2 Instead of flocked polyether ester, Moko melting point is 13
80 polybutylene terephthalate neuisophthalate (
A powder mixture was prepared in the same manner as in Example 1 using a 50/50) copolymer and a polybutylene terephthalate/poly(tetramethylene oxide) glycol (50/50) copolymer 'B- having a melting point of 185°C. made.

The copolymerized polyester was obtained as a long sheet in the same manner as the block polyether ester in Example 1, but the copolymer {B'' could not be kneaded if it was less than 19,000.
In the case of extrusion exceeding 0.000, the foaming agent decomposed and could not be taken off as a sheet.

A sheet of copolymerized polyester arc was irradiated with an electron beam in the same manner as in Example 1, and then heated and foamed, but the sheet was deformed and almost no vaporized gas was trapped inside, making it impossible to form a foamed sheet. 12,000 tetralin was almost completely dissolved, indicating that this copolymer was not effectively crosslinked by electron beam irradiation.

Claims (1)

[Claims] 1. A block polyether ester with a melting point of 100 to 180°C mainly composed of butylene terephthalate units and poly(alkylene oxide) glycol units is mixed with azodicarbonamide to form a sheet-like product, and then 0.0% is added to this sheet-like product. A method for producing a sheet-like polyester elastomer foam, which comprises irradiating it with ionizing radiation of 2 to 50 Mrad to impart a crosslinked structure, and then foaming it by heating it to a temperature higher than the decomposition temperature of azodicarbonamide.