Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
2002-04-12
2004-06-08
Foelak, Morton (Department: 1711)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S070000, C428S071000, C521S057000, C521S069000, C521S070000, C521S072000
Reexamination Certificate
active
06746759
ABSTRACT:
The invention relates to cellular plastic materials.
INTRODUCTION
There are several classes of thermosetting resin system that could be considered as possible candidate materials for the production of fire resistant low-density cellular insulation foam when compounded with appropriate additives. However, the required flammability performance restricts selection of many types of organic thermosetting resin. For instance, halogen atoms would need to be incorporated into the chemical backbone of unsaturated polyester resins and epoxy resins to impart self-extinguishing behaviour. Alternatively, unsaturated polyester resins and epoxy resins would need to be blended with halogenated compounds to impart self-extinguishing behaviour. Such chemical compositions would generate toxic gases such as hydrogen chloride or hydrogen bromide in a fire situation. Addition of other types of non-halogenated flame-retardant such as organo-phosphorous compounds can give rise to high smoke emission in a fire situation. The addition of a flame-retardant compound may also have an adverse effect on cellular plastic mechanical strength. Other, thermosetting resins such as polyurethane and polyisocyanurate resins produce high smoke and toxic gas emissions in a fire situation Polyurethane may not be self-extinguishing in a fire situation. Hence these materials cannot be the materials of choice if fire performance is a concern.
Historically, phenolic resins have been the preferred thermosetting plastic material when low smoke emission and self-extinguishing ability are of paramount importance in a particular application.
Presently, in cellular foam manufacture, a phenolic resole resin is commonly catalysed by either a strong organic or inorganic acid. For example DE3329334 A describes a process for the production of an acid cured phenol resin foam in which the acids are premixed with novalak resin before addition of a phenolic resole. The selection of acid type is dependent on the desired curing time and temperature. Cellular insulation foam is produced when the blowing agent that has been pre-blended into the resin, starts to boil. Halocarbons are commonly used blowing agents. Expansion typically occurs in the temperature range 25° C. to 80° C. In thick sections of acid cured phenolic foam, it is possible that a resin exotherm will develop. The occurrence of an uncontrolled exothermic chemical reaction is more likely when a strong acid is used as catalyst. When exothermic reactions develop, large amounts of water or steam are created by the phenolic resins condensation polymerisation reaction. The consequential shrinkage of the resin matrix can adversely affect the ability to form a closed cell foam structure as well as impairing the mechanical strength performance. Closed cell foam structure is highly desirable to maximise insulation performance.
As conventional phenolic foam is produced using an acid catalyst, there has been concern that when this foam is in direct contact with metal, such as an insulated pipe, it could induce corrosion of the metal. Hence there is a desire for a foam insulation product that has the mechanical strength and fire performance of an acid catalysed phenolic foam, yet is pH neutral or moderately basic. Such a material would alleviate the risk of induced acidic corrosion.
EP-A-0166275 describes a resin composition for a molding material used particularly for electrically insulating laminated plates. The resin comprises a resole phenolic resin, an epoxy resin and a strength enhancing amine compound.
It is well known that alkaline phenol formaldehyde resole resins can be cured by aliphatic esters to produce a chemical binder for foundry sand moulds and cores as described in JP-A-130627/1975 and EP-A-O 085 512. Also, U.S. Pat. No. 3,599,433 and U.S. Pat. No. 3,696,622 discuss alkaline phenol formaldehyde resole resins reacting with a lactone as a method for soil stabilisation and leakage prevention. It has been documented in EP-A-0146499, JP-A-S62-250267, JP-A-04364908 and JP 01092242A that acid free phenolic cellular plastic can be produced by curing an alkaline phenol formaldehyde resin with various aliphatic esters.
Other commercial applications using alkaline phenol formaldehyde resins cured by aliphatic esters such as lactones have been limited due to the inherent high shrinkage of the cured phenolic resin.
There is a need for a stable cellular plastic foam that has good mechanical strength and fire performance.
STATEMENTS OF INVENTION
According to the invention there is provided a resin mixture for forming a cellular plastic foam, the resin mixture containing a phenolic resole, a chain extending agent, and as curing agents, a base, and an ester and/or an aliphatic carbonate.
In one embodiment the chain-extending agent is an epoxy resin.
In another embodiment the chain-extending agent is a thermoplastic modifier.
In a particularly preferred embodiment the chain extending agent includes an epoxy resin and a thermoplastic modifier.
Preferably the thermoplastic modifier is a phenolic novalak resin.
Preferably the phenolic novalak has a number average molecular weight between 1000 and 1500.
Preferably the phenolic novalak is present in an amount from 2% to 30% by weight. Most preferably in an amount from 14 to 25% by weight.
In one embodiment of the invention the resin mixture has a pH of at least 9.
In one embodiment the epoxy is present in an amount from 2% to 30% by weight.
Preferably the epoxy resin contains at least two epoxy groups in the molecule.
The epoxy is preferably based on oligomers of diglycidylether of Bisphenol A or diglycidylether of Bisphenol F or mixtures thereof.
Preferably the phenolic resole has a reactive solids content in the range of from 50% to 85% by weight.
In one embodiment the phenolic resole is prepared from an optionally substituted phenol and an aldehyde in the molar ratio of phenol to aldehyde of 1:1 to 1:3.0
Typically the base is potassium hydroxide and/or sodium hydroxide.
Preferably the ester is a lactone. Ideally the ester is selected from one or more of &ggr;-butyrolactone and caprolactone.
Preferably the ester is present in an amount of from 2 to 25% by weight.
In one embodiment the resin mixture includes a blowing agent. The blowing agent may be a liquid and/or a gas.
Preferably the blowing agent has a boiling point of up to 70° C.
In a preferred embodiment the blowing agent is present in the resin mixture in an amount of up to 25% by weight.
Preferably the blowing agent is a halogenated hydrocarbon, especially pentafluorobutane and/or 1,2 dichloro-1-fluoroethane and/or pentane or mixtures thereof.
In one embodiment the resin mixture includes a surfactant, especially a non-ionic surfactant.
The surfactant may be a dimethylsiloxane/polyoxyalkylene copolymer.
Preferably the surfactant is present in an amount of from 1 to 15% by weight. The invention also provides a process for the preparation of a cellular plastic by expanding and curing a resin mixture of the invention.
In one embodiment the cellular plastic is manufactured at atmospheric pressure.
Alternatively the cellular plastic is manufactured at a pressure less than atmospheric pressure.
In another embodiment the cellular plastic is manufactured at a pressure greater than atmospheric pressure.
The invention further provides a cellular plastic whenever manufactured using a resin mixture of the invention and/or using a process of the invention.
Preferably the cellular plastic has a thermal conductivity of less than 0.04 W/mK, most preferably less than 0.025 W/mK.
Preferably the cellular plastic for insulation has a substantially closed cell structure, ideally having a closed cell content of greater than 90%. Most preferably this closed cell structure is stable over an extended period of time at room temperature.
DETAILED DESCRIPTION
The materials described herein relate to formulated phenolic resin compositions. These compositions can be used to manufacture closed cell insulation foam that is self-extinguishing in a fire situation. Also this cellular insulation foam generates low smo
Coppock Vincent
Edgerley Graham Morgan
Harris Mark Stanley
Ryder Norman
Foelak Morton
Jacobson & Holman PLLC
Kingspan Industrial Insulation Limited
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