Phenol foam

Details Phenol foam Phenol foam

2000-08-17

2003-07-01

Foelak, Morton (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Cellular products or processes of preparing a cellular...

C521S098000, C521S129000, C521S131000, C521S181000

Reexamination Certificate

active

06586484

ABSTRACT:

TECHNICAL FIELD
This invention pertains to a type of phenol foam which can be used preferably for heat insulation as various materials for construction.
BACKGROUND ART
Among various types of organic resin foams, the phenol foam has excellent fire-retarding property, high heat resistance, low fuming property, high dimensional stability, high solvent resistance, and good processability. Consequently, it is widely used in various types of construction materials. Usually, the phenol foam is manufactured by blending the resol resin, which is prepared by condensation of phenol and formalin in the presence of an alkaline catalyst, with foaming agent, surfactant, curing catalyst, and other additives homogeneously, followed by foaming.
For the conventional phenol foam, the foaming agents that can be used include trichlorotrifluoroethane (CFC-113), trichloromonofluoromethane (CFC-11), dichlorotrifluoroethane (HCFC-123), dichlorofluoroethane (HCFC-141b), and other halogenated hydrocarbons and their derivatives. For these types of halogenated hydrocarbons and their derivatives for use as a foaming agent, the safety in manufacturing is high, and the thermoconductivity of the gas itself is low, so that the thermal conductivity of the obtained foam is also low. This is an advantage. However, at present, it has become clear that CFC-113, CFC-11, and other chlorine atom-containing substances can decompose ozone in the stratosphere and damage ozone in the ozonosphere, and the damages of these substances on the environment of the earth have become a world problem. Consequently, their manufacturing and use are under control in the world. Also, even for fluorohydrocarbons 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a), etc., free of chlorine and having null ozone-damaging coefficient, as they have relatively high earth greenhouse effect coefficients, it seems that their use might be restricted in Europe. Consequently, pentane and other hydrocarbons have come under spotlight (as a substitute).
In the past, it was known that n-pentane and cyclopentane may be used as a foaming agent for the phenol foam. However, although these hydrocarbons do not harm the ozonosphere and have relatively small earth greenhouse effect coefficients compared with the halogenated hydrocarbons, the average pore size of the foam formed becomes larger, the thermal conductivity of the gas itself is high so that no good heat-insulating performance can be realized, and the pore walls are weak and the compressive strength and other mechanical strengths are also insufficient. These are troubles that hamper their practical applications.
In this respect, Japanese Tokuhyo Patent No. Hei 4[1992]-503829 disclosed a method for manufacturing phenol foam with even lower thermal conductivity by using a mixture of a prescribed type of fluoroalkane (referred to as PFA hereinafter) and alkane or cycloalkane as the foaming agent. However, the fluoroalkane also has a relatively large earth greenhouse effect coefficient just as the aforementioned fluorohydrocarbon, so that its use may also be restricted.
Also, Japanese Kokai Patent Application No. Hei 3[1991]-231940 disclosed a method for manufacturing a phenol foam by using polyfluorotrialkylamine as the foaming agent. However, although perfluorotrialkylamine has a low thermal conductivity of the gas itself and a relatively small coefficient of the earth greenhouse effect, it has been found by the present inventors that when phenol foam is test-made by using perfluorotrialkylamine having methyl or ethyl as the fluorocarbon in the molecules, the cell size of the formed phenol foam becomes larger so that the heat-insulating performance is not good, the rigidity of the phenol foam becomes lower, and the compressive strength and other mechanical strengths of the foam are lower. On the other hand, when the phenol foam is test-made by using perfluorotrialkylamine having butyl or other fluorocarbon having an even higher boiling point as the foaming agent at a foaming temperature of 100° C. or lower, good foaming cannot be achieved, and satisfactory phenol foam cannot be formed.
DISCLOSURE OF INVENTION
The purpose of this invention is to solve the aforementioned problems of the conventional technology. That is, the purpose of this invention is to provide a type of phenol foam which is manufactured using a hydrocarbon as the foaming agent, and which has excellent heat-insulating performance, high compressive strength and other mechanical strengths, improved brittleness, and is friendly to the environment of the earth.
Means to Solve the Problems
To realize the aforementioned purpose, the present inventors have performed extensive research. As a result of this research, a type of phenol foam meeting the aforementioned requirements was discovered, and this invention was reached.
That is, this invention provides the following type of phenol resin foam heat-insulating material:
1. A type of phenol resin foam heat-insulating material, characterized by the following facts: the phenol foam has an independent porosity of at least 80%, an average pore size in the range of 10-400 mm, and a thermal conductivity of 0.025 kcal/mhr° C. or lower; the phenol foam is composed of a portion of pores filled with a gas containing C
4-6
saturated hydrocarbon and a resin portion made of a phenol resin containing 0.01-5 wt % of at least one type of fluoroamine represented by the following formula (1):
(C
a
F
b
)
3
N  (1)
In formula (1), a is a natural number of 4 or larger and b is 2a+1.
2. The phenol resin foam heat-insulating material described in claim 1, characterized by the fact that the weight of the gas filled in the portion of pores is in the range of 2-35 wt % of phenol foam.
3. The phenol foam described in claim 1 or 2, characterized by the fact that the phenol foam has a density in the range of 10-70 kg/m
3
, a brittleness of 30% or smaller, and a compressive strength meeting the relationship shown in formula (2) with respect to the density:
compressive strength (kg/cm
2
)≧density (kg/m
3
)×0.1164−2.5  (2).
In the following, this invention will be explained in more detail.
The phenol foam of this invention is composed of a portion of pores filled with a gas and a resin portion made of walls of pores and the base material. For the phenol foam of this invention, the independent porosity has to be at least 80%, or preferably at least 85%, or more preferably 90%. If the independent porosity is lower than 80%, the foaming agent of the phenol foam may be substituted with air, so that the heat-insulating performance deteriorates significantly over time. Also, the brittleness of the surface of the foam becomes more serious, so that the mechanical properties of the foam may not be able to meet the demand for the practical applications.
For the phenol foam of this invention, the average pore size should be in the range of 10-400 mm, or preferably in the range of 20-200 mm. If the average pore size is smaller than 10 mm, as there is a limit to the thickness of the pore walls, the foam density naturally rises. As a result, the heat transfer proportion of the resin portion in the foam rises, and the heat-insulating performance of the phenol foam may become insufficient. On the other hand, if the average pore size becomes larger than 400 mm, the beat transfer due to radiation rises, and the heat-insulating performance of the foam also may deteriorate.
In the phenol foam of this invention, C
4-6
alkane or cycloalkane is used as the foaming agent, that is, the gas to fill in the portion of pores. Examples include n-butane, isobutane, n-pentane, isopentane, cyclopentane, neopentane, n-hexane, isohexane, 2,2-dimethylbutane, 2,3-dimethylbutane, cyclohexane, etc. Among them, n-butane, isobutane, n-pentane, isopentane, cyclopentane, neopentane, and other butanes and pentanes are preferred in this invention. According to this invention, it is also possible to make use of a mixture of two or more types of hydrocarbons. Examples of the mixtures that can be

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