Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent

Definitions

• the invention relates to a process for the production of ge foamed plastics, in which a starting mixture of monomeric, oligomeric or polymeric compounds "polymerized with vinyl grouping in the presence of a blowing agent and a catalyst and then foamed by irradiation.
• a process for the manufacture of articles from polymethyl methacrylate in which a mixture of methyl methacrylate monomer, preferably liquid blowing agent and catalyst is polymerized to a solid body containing blowing agent in a first stage. This is carried out in a second stage foamed by heating to the softening temperature of the plastic, for example by means of microwaves.
• the acrylate polymers produced in this way are very difficult to foam with microwaves. In a commercially available microwave oven, the known material only begins after about 30 minutes to become soft and to inflate very slowly.
• GB-PS 1 348 552 describes a method for producing foams in which compounds containing vinyl groups are polymerized in the presence of a blowing agent, a catalyst and additionally a crosslinking agent.
• the polymers are foamed using radio waves of approximately 27 MHz. It is particularly pointed out that a crosslinking agent is necessary in order to be able to obtain a foamed material. If microwave radiation is used instead of radio waves in this process, no satisfactory results are obtained either. If the addition of crosslinking agents is dispensed with, the result is products which are too soft and are not stable foams.
• the present invention is based on the object of specifying a method with which the products can be fully foamed in a maximum of 5 minutes without the addition of crosslinking agents.
• the starting mixture is composed of at least three components, which consist of a component A of monomeric methyl methacrylate and / or styrene, optionally with a proportion of prepolymerized methyl methacrylate and / or styrene, of a component B consists of monomeric or oligomeric compounds containing a vinyl grouping and microwave-sensitive groups and a component C consists of monomeric, oligomeric or polymeric compounds containing microwave-sensitive groups without vinyl grouping, components B and C containing hydroxyl, thiol , Alkylamino- with 1 to 6 carbon atoms, amino or carboxyl groups are substituted, and that foaming by microwave radiation lung is brought about.
• a component A of monomeric methyl methacrylate and / or styrene optionally with a proportion of prepolymerized methyl methacrylate and / or styrene
• a component B consists of monomeric or oligomeric compounds containing a vinyl group
• the starting mixture has a special composition.
• the mixture component is methyl methacrylate and / or styrene. Some of these compounds can also be present in prepolymerized form.
• the amount of component A in the starting mixture is 50 to 95% by weight, preferably 70 to 8% by weight, based on the total weight of the starting mixture, i.e. without taking into account the proportions of blowing agent, catalyst and fillers or dyes that may also be present.
• the mixture components B and C can be monomeric, oligomeric or polymeric compounds and contain groups which are easily excitable by microwaves. Such groups are hydroxyl, thiol, alkylamino, amino or carboxyl groups.
• Component B furthermore has at least one vinyl grouping, while component C is free of vinyl groupings. It is also essential that the main part of the starting mixture forms methyl methacrylate and or styrene.
• the amount of component B i of the starting mixture is 5 to 50% by weight, preferably 10 to 2% by weight. -%, based on the total weight of the starting mixture.
• the amount of component C is 1 to 20% by weight. preferably 2 to 7% by weight, based on the total weight of the starting mixture.
• Hydroxyalkyl acrylates or methacrylates and / or hydroxyalkenes are preferably used as component B. Hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxybutyl acrylate, hydroxybutyl ethacrylate and allyl alcohol are particularly suitable fetch As component C, for example, hydroxyl-containing silicones, polyesters, ie polyols, melamine resin or urea precondensates are used. Particularly good results are achieved with silicones. Bisphenol A, nonylphenol, decanol and perfluoroalcohol are also suitable.
• Solid blowing agents can be used, which decompose when the temperature rises and thereby release the expanding gases.
• Liquid blowing agents are preferably used which have a boiling point of max. 100 ° C., preferably 50 ° C., evaporate when the temperature of the material rises and thereby inflate the material.
• the products contain 5 to 60 units. -%, preferably 40 to 50 wt. -% blowing agent, based on the total remaining portions in the reaction mixture. Frigen 1 and a mixture of Frigen 11 and Frigen 114 are preferably used.
• a conventional peroxide catalyst can be used as the polymerization initiator, which is effective when heated. If, for the purpose of polymerization, the reaction mixture has to be heated to a temperature above the evaporation temperature of the blowing agent, the polymerization can be carried out under pressure in order to prevent the blowing agent from being released prematurely.
• a photoinitiator is preferably used as the polymerization catalyst, which makes it possible to polymerize the mixture at low temperature, in particular at about room temperature, by exposure to radiation matched to a photoinitiator known for acrylate monomer, for example UV light of a wavelength of 350 nm.
• the polymerization can be controlled by switching the radiation sources on and off or by external cooling so that the temperature in the mass to be polymerized does not rise above a certain value in the course of the exothermic polymerization reaction which is below the evaporation temperature of the liquid blowing agent.
• fillers and / or dyes can be provided in the starting mixture, which can be selected depending on the area of use of the foamed product.
• An already polymerized, propellant-containing product can be stored as an intermediate product if it is not immediately fed into the second process stage, in which it is foamed by microwave radiation of approximately 2000 to 3000 MHz.
• the method according to the invention enables the products to be foamed by means of microwaves in a maximum of 5 minutes. Most of the products are fully foamed after only 2 minutes.
• non-substituted monomeric or prepolymeric vinyl compounds i.e. Methyl methacrylate and / or styrene, fast foaming products are thus obtained which also have well-formed pores.
• the foamed polymers according to the invention can also be transparent and in the form of sheets, sheets, moldings and multilayer bodies with a foam core.
• blowing agent Frigen 11
• the resulting blowing agent-containing polymer is then foamed by heating by means of high frequency in a commercially available microwave oven (2450 MHz, 720 W output power). The process of exhaustion was over after a minute.
• Example 1 The procedure of Example 1 is repeated using 4 parts of methyl methacrylate, 0.55 part of hydroxybutyl acrylate, 0.45 part of silicone, 0.05 part of nonylphenol, 0.03 part of UV polymerization initiator and 2.5 parts of blowing agent (Frigen 11) become. The polymer was fully foamed after about 2 minutes.
• Example 1 The procedure of Example 1 is repeated, except that 2.5 parts of methyl methacrylate, 1 part of styrene, 1 part of hydroxybutyl methacrylate, 0.25 part of nonylphenol, 0.25 part of bisphenol ⁇ , 0.07 part of UV polymerization initiator and 2 , 5 parts of blowing agent can be used.
• the duration of the foaming process using microwave radiation was less than 2 minutes.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

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• 1985
  • 1985-09-11 DE DE19853532347 patent/DE3532347A1/de active Granted
• 1986
  • 1986-08-08 WO PCT/EP1986/000471 patent/WO1987001710A1/de not_active Ceased
  • 1986-08-08 EP EP19860904821 patent/EP0236353A1/de active Pending

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