Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2001-11-27
2003-04-01
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C428S304400, C428S319100, C428S422800, C521S112000, C521S130000, C521S136000, C521S137000, C521S902000
Reexamination Certificate
active
06541530
ABSTRACT:
The present invention relates to a urethane-modified polyisocyanurate foam having a high expansion rate, which is excellent in flame retardancy and heat resistance, and is low in smoke generation, without using chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs) as a blowing agent.
In the polyurethane and polyisocyanurate industries, because of a problem of depleting the ozone layer, use of CFCs, which had been used as versatile and effective blowing agents, has been banned since 1995, and further, even HCFCs, substitutes for CFCs, having much lower ozone depletion potential, are scheduled to be banned from the year of 2003. Hence, a variety of alternative blowing agents, such as hydrofluorocarbons (HFC), hydrocarbons (HC), carbon dioxide (CO
2
), etc. are being studied.
It is said lately that HCFC blowing is being replaced by the CO
2
blowing for the polyurethane foam (PUR system) for insulated metal sidings or panels, and that the replacement has been almost completed.
However, in the case of the polyisocyanurate foam (PIR system), which is rated high for the flame retardancy and heat resistance, when the CO
2
blowing method is applied, there are specific problems of lower than typical flame retardancy, heat resistance and shrinkage (deformation) with time, in addition to a problem of unsatisfactory adhesion to a facing material, not allowing the replacement of the conventional blowing method by the CO
2
blowing to develop as successfully as in the case of PUR systems.
In the CO
2
blowing method, it is generally said that a foam causes shrinkage (deformation) with time. This is because of the rapid diffusion of CO
2
from the foam cells.
In the field of insulated metal sidings or panels cored with the PUR system, the replacement by the CO
2
blowing method has been almost completed by lowering a closed cell ratio as a means for preventing shrinkage (deformation) with time. For example, by employing a combination of a high molecular polyol and a low molecular polyol, the resulting foam becomes rich with open cells and, because of its low density, does not cause shrinkage.
In the field of insulated metal sidings or panels cored with the PIR system, a foam having an open cell structure can be obtained to prevent shrinkage (deformation) by employing a method of using certain aromatic polyester polyols (JP-A-10-231345), and a method of producing a foam of relatively low density by using a trimerization catalyst and a carbodiimide-forming catalyst in combination (Japanese Patent No. 2,972,523), but there are problems of lowering flame retardancy, heat resistance and a poor adhesion to a facing material, and it is therefore difficult to use the CO
2
blowing as a substitute for the conventional blowing methods.
In order to solve the above-mentioned problems of a PIR type foam employing a CO
2
blowing agent, it is necessary not only to make a foam having a continuous cell phase (open cells) for improving the shrinkage problem but also to solve the above-mentioned problems concerning flame retardancy and heat resistance.
In order to solve the above-mentioned problems, the present inventors have discovered a novel method not only for freely controlling a cell size but also for improving flame retardancy and heat resistance by applying a benzylic ether type phenolic resin (hereinafter referred to as “BEP”) to the PIR system.
Particularly, flame retardancy and heat resistance are improved by employing BEP as a polyol component and a cell size is controlled by mixing surfactants, having different properties, at an appropriate ratio. For example, a silicone type surfactant is used as a foam stabilizer (1) and a dimethylsilicone oil is used as a foam stabilizer (2).
More particularly, the present invention provides a urethane-modified polyisocyanurate foam obtained by reacting (A) a polyisocyanate compound component, (B) a polyol component (said polyol component contains a modified phenolic resin (hereinafter referred to as “modified BEP”) obtained by adding 20 to 100 parts by weight of a polyhydric alcohol or its alkylene oxide adduct to 100 parts by weight of a benzylic ether type phenolic resin and heating under a reduced pressure, in an amount of at least 3 wt % to the total resin component), (C) water and (D) a foam stabilizer comprising a mixture of at least 2 silicone type surfactants having different surface tensions wherein a surfactant having a higher surface tension has a surface tension of higher than 22 dyne/cm and a surfactant having a lower surface tension has a surface tension of at most 22 dyne/cm, in the presence of (E) a urethane-forming catalyst and/or a trimerization catalyst.
The polyol component (B) used in the present invention is a mixture of modified BEP and a polyol generally used for producing a urethane foam. Thus, the polyol component (B) comprises mainly modified BEP by adding 20 to 100 parts by weight of a polyhydric alcohol or its alkylene oxide adduct to 100 parts by weight of a benzylic ether type phenolic resin and heating the mixture under a reduced pressure, as described in JP-B-7-30155. Examples of other polyols usable with the modified BEP include difunctional polyols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, polytetramethylene glycol, 1,4-butanediol or these difunctional polyols addition-polymerized with one or two or more kinds of alkylene oxides, trifunctional polyols such as trimethylolpropane, glycerin or these trifunctional polyols addition-polymerized with alkylene oxides, polyfunctional polyols such as pentaerythritol, sorbitol, sugar or these polyfunctional polyols addition-polymerized with an alkylene oxide, an aromatic polyester polyol, an acryl polyol resin, and the like, and these polyols may be used alone or may be used in a mixture of two or more polyols. The modified BEP is used suitably in an amount of at least 3.0 wt to the total resin component. If the amount of the modified BEP is less than 3.0 wt %, flame retardancy, heat resistance and low smoking property become poor.
A polyisocyanate compound (A) used in the present invention is not specially limited and may be ones generally used in the preparation of a polyurethane foam, examples of which include m- or p-phenylene diisocyanate, p-xylene diisocyanate, ethylene diisocyanate, tetramethylene 1,4-diisocyanate, hexamethylene-1,6-diisocyanate, diphenylmethane-4,4′-diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, 3,3-dichloro-4,4′-biphenylene diisocyanate or 1,5-naphthalene diisocyanate, 2,4- and 2,6-tolylene diisocyanate and their mixture, crude tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, crude diphenylmethane diisocyanate, and the like. These isocyanate compounds may be used alone or in a mixture of two or more. Its amount used is an equivalent ratio of an isocyanate group/active hydrogen in a polyol component mixture solution in a range of from 1.05 to 5.0, preferably from 1.50 to 3.0. If the above equivalent ratio is less than 1.05, flame retardancy, heat resistance and low smoking property become poor, and if the equivalent ratio is more than 5.0, a foam produced becomes brittle and adhesiveness to a facing material becomes poor.
A foam stabilizer used in the present invention is a mixture of at least two kinds of silicone type surfactants having different surface tensions, and a component having a higher surface tension has a surface tension higher than 22 dyne/cm. A foam stabilizer generally used in the preparation of a urethane foam may be used, preferable example of which include an organic polysiloxane copolymer, a polydimethylsiloxane·polyalkylene oxide adduct, a vinylsilane·polyoxyalkylene polyol compound and the like. A component having a lower surface tension has a surface tension lower than 22 dyne/cm, preferable examples of which include a dimethylsilicone oil.
Examples of the organic polysiloxane copolymer include SH-190, SH-192, SH-193, SH-194, M505, M507, M509 and SRX253 manufactured by Toray Silicone K.K., L-
Nakamura Tsutomu
Sato Tsuyoshi
Hodogaya Chemical Co. Ltd.
Sergent Rabon
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