Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-03-30
2004-03-30
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S131000, C521S170000, C521S174000
Reexamination Certificate
active
06713521
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of preparing a rigid polyurethane foam, and a composition for rigid polyurethane foam. The rigid polyurethane foam can be utilized as thermally insulating material for freezers, refrigerators, buildings and the like.
BACKGROUND OF THE INVENTION
Rigid polyurethane foam has widely been used as thermally insulating material for refrigerators, e.g. domestic refrigerator, because of low product density, excellent insulating properties and high mechanical strength.
As the blowing agent for production of rigid polyurethane foam, halogen-substituted chlorofluorocarbon (hereinafter abbreviated to CFC), particularly trichlorofluoromethane, R-11) has hitherto been used.
However, since this blowing agent R-11 contains halogen, there is a fear that environmental pollution or disruption such as possibility of depletion of the ozone layer in the stratosphere and global warming are caused. For the purpose of protecting the global environment, the production and consumption of CFC are controlled in the world.
DETAILED DESCRIPTION OF THE INVENTION
In Japan, the production of CFC had been prohibited before the end of 1995. As a novel blowing agent as a substitute, for example, hydrochlorofluorocarbon (HCFC) having a small ozone depletion coefficient is used. For example, HCFC-141b (1,1-dichloro-1-fluoroethane), HCFC-22 (chlorodifluoromethane) and HCFC-142b (1-chloro-1,1-difluoroethane) are introduced and applied as the blowing agent.
However, HCFC as a substitute of CFC exerts a small influence on the ozone layer, but still has characteristics of depleting the ozone layer, because chlorine atoms are contained in the molecule. A reduction in service amount of HCFC is performed by stages. Accordingly, use of a blowing agent having no influence on depletion of the ozone layer has been suggested now in view of the protection of the global environment. In some applications, there has already been introduced and applied a blowing agent which contains no chlorine atom to be secured against depletion of the ozone layer, e.g. cyclopentane.
However, cyclopentane is a blowing agent, which does not exert a harmful influence on the global environment, but has some problems. The thermal conductivity of a cyclopentane gas itself is comparatively high and insulating performances of a rigid polyurethane foam using cyclopentane are inferior to those of a conventional foam using HCFC-141b and, therefore, an improvement in thermally insulating performances is required. Particularly, an improvement in thermally insulating performances at a low temperature range is required. Cyclopentane itself is hardly soluble in a conventionally used polyol and, when using a large amount of cyclopentane to reduce the density of the foam, the stability of a premix is poor. On the other hand, there is suggested a technique of preparing a so-called emulsion foam by mechanically dispersing a comparatively large amount of cyclopentane in a polyol (Japanese Patent Application No. 10-303794(303794/1998)), and the resulting emulsion foam exhibits comparatively good insulating characteristics at a low temperature range. However, this technique requires a special equipment.
To solve these problems and to produce a thermally insulating material having improved thermal conductivity, the thermal conductivity of the rigid foam as a product can be reduced by using, as a blowing agent, a mixture of a considerably large amount of cyclopentane and a small amount of water. That is, the thermal conductivity can be reduced by preparing a cyclopentane-rich gas in a cell. By using, as a main portion of a polyol, a polyether polyol prepared by addition-polymerizing an alkylene oxide to o-toluenediamine as an initiator, a stable premix can be prepared even if a large amount of the blowing agent is dissolved in the polyol. Therefore, the density of the foam can be reduced.
The present invention provides a method of preparing a rigid polyurethane foam from a composition comprising an aromatic polyisocyanate, a polyol, a blowing agent, a catalyst, a surfactant and other aids, characterized in that the blowing agent is a combination of cyclopentane and water, and the polyol contains a polyether polyol prepared by addition-polymerizing an alkylene oxide to o-toluenediamine as an initiator.
The present invention also provides a composition for rigid polyurethane foam, comprising:
(1) an aromatic polyisocyanate,
(2) a polyol containing a polyether polyol prepared by addition-polymerizing an alkylene oxide to o-toluenediamine as an initiator,
(3) a blowing agent comprising cyclopentane and water, and
(4) a catalyst, a surfactant and other aids.
A rigid polyurethane foam to be used as thermally insulating material for refrigerators can be produced from this composition.
The aromatic polyisocyanate (1), for example, polyisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and polymethylene polyphenyl polyisocyanate (polymeric MDI) and modified polyisocyanates thereof may be used alone or in combination.
A modified polyvalent isocyanate, i.e. a product obtained by a partial chemical reaction of organic di- and/or polyisocyanates can be used. For example, there can be used di- and/or polyisocyanates, which contain an ester, urea, buret, allophanate, carbodiimide, isocyanurate and/or urethane group can be used.
The amount of the aromatic polyisocyanate (1) in the composition may be within a range from 100 to 140 parts by weight, preferably from 115 to 140 parts by weight, particularly from 120 to 130 parts by weight, based on 100 parts by weight of the polyol.
A polyol (2), a blowing agent (3) and an aid (4) constitute a polyol mixture.
The polyol (2) is preferably a polyether polyol and/or a polyester polyol. The polyether polyol is obtained by addition-polymerizing an alkylene oxide (e.g. propylene oxide and/or ethylene oxide) to a reactive starting material, for example, a polyhydric alcohol such as ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, sucrose and bisphenol A; or an aliphatic amine such as triethanolamine and ethylenediamine, or an aromatic amine such as toluenediamine and methylenedianiline (MDA).
The polyether polyol can be obtained by addition-polymerizing an alkylene oxide to a reactive starting material containing 2-8 reactive hydrogen atoms, preferably 3-8 reactive hydrogen atoms, in the molecule by anionic polymerization in the presence of a catalyst such as alkali hydroxide (e.g. potassium hydroxide and sodium hydroxide) or alkali alcoholate (e.g. potassium methylate and sodium methylate) using a conventionally known method. The polyether polyol can be obtained by adding an alkylene oxide to a reaction starting material due to cationic polymerization in the presence of a catalyst such as Lewis acid (e.g. antimony pentachloride and boron fluoride etherate).
Suitable alkylene oxide includes, for example, tetrahydrofuran, ethylene oxide, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide, 1,2-propylene oxide and styrene oxide. Among them, ethylene oxide and 1,2-propylene oxide are particularly preferred. These alkylene oxides can be used alone or in combination.
The reactive starting material (i.e. initiator) includes, for example, polyhydric alcohols (e.g. ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, sucrose and bisphenol A), alkanolamines (e.g. ethanolamine, diethanolamine, N-methyl- and N-ethyl-ethanolamine, N-methyl- and N-ethyl-diethanolamine, triethanolamine), and ammonia. Furthermore, aliphatic amines and aromatic amines can be used. Examples thereof include ethylenediamine, diethylenetriamine, 1,3-propylenediamine, 1,3- or 1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexamethylenediamine, phenylenediamine, o-toluenediamine, m-toluenediamine, methylenedianiline (MDA) and polymethylenedianiline (P-MDA).
As the polyester polyol, there can be used, for example, a polyester polyol such as polyethylene terephthalate, which is prepared from a polycarboxylic ac
Chiba Takanori
Matsumoto Takuya
Ono Keiji
Shimizu Takehiro
Bayer Aktiengesellschaft
Cooney Jr. John M.
Gil Joseph C.
Mrozinski, Jr. John E.
LandOfFree
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