DD218898A1 - PROCESS FOR PREPARING LAYER BODIES HIGH THERMOSTABILITY - Google Patents

Abstract

Process for the production of layered bodies of high thermal stability on the basis of the use of epoxy resins. The solution according to the invention should make it possible to produce thermostable layer bodies by means of suitable carrier materials by impregnation and compression, to improve the durability of the impregnation solutions and to ensure the storage stability of the technologically conditioned intermediate products. This is achieved by mixing epoxy resin with an epoxy equivalent of greater than 300 with polyisocyanates having a functionality of greater than or equal to 2 in an isocyanate / epoxy equivalent ratio of 2: 1 to 10: 1 and after applying this mixture to carrier material or impraining Traeger material is pre-crosslinked using a temperature of greater than 80 C. The invention can be applied in all fields of technology in which reaction resin compositions are used for impregnating.

Description

Title of the invention

Process for the production of laminates of high thermal stability

Field of application of the invention

The invention relates to a process for the production of laminates of high Ihermostability in the form of carrier layers (functional and passive coatings) and panels, pipes, tapes and profiles (laminates) based on the use of epoxy resins for applications as construction and electrical insulating materials, Thermal barrier coatings and functional coatings with increased resistance to corrosion, moisture and chemicals ·

The areas of application are the electrotechnical, electronic industry, the scientific instrument industry, the mechanical engineering and other sectors of the national economy ·

Characteristic of the known technical solutions

It is known to produce laminates by impregnation of support materials and drying of these materials and by subsequent pressing of these prepregs at higher, serving for crosslinking temperatures · They use of inorganic support materials such as glass silk, mica, asbestos leads to an increase in the

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However, the thermostability of the laminates is also substantially determined by the binder used. In the customary use of epoxy resins as binders, acid anhydrides and polyamines serve as crosslinking component. Β Bs form laminates which have a construction temperature resistance of <130 ⁰ C, since prolonged use at higher temperatures causes degradation of the binder and, in conjunction therewith, pronounced deterioration of the properties.

According to DE-AS 2359386, polymers with high thermal stability can be prepared by reacting polyepoxides with polyisocyanates using bnidazole and morpholine derivatives as accelerators. "Application of the DB-AS 2359386 corresponding material compositions in conjunction with solvents necessary for the production of impregnating solutions results however, no usable impregnation solutions, because in too short a time too much increase in viscosity occurs during impregnation «

Stable impregnation solutions are obtained according to DE-OS 3148358, when hydroxy-containing epoxy compounds are used in combination with isocyanate compounds. "At least one equivalent of hydroxyl must be added to one equivalent of isocyanate for complete urethane formation." Dissociation of the urethane bonds at higher temperatures eventually results in final cure converts the regenerated isocyanate groups through reaction with epoxy groups into oxazolidone rings which provide higher thermal stability compared to the conventional cured epoxy resins

Object of the invention

The inventive solution should make it possible to coat or impregnate threadlike or sheetlike, organic or inorganic carrier materials, so that thermostable coatings, laminates (laminating substances) and the like may be produced under higher temperatures, if necessary under pressure. Reinforced Plastmeterialien can be produced and both the impregnation solutions under given conditions have suitable durability and the storage stability of technological intermediates (prepregs) is ensured ·

Explanation of the essence of the invention,

The object of the invention is to apply reaction components dissolved in suitable solvents to support materials and to place them in a prepolymer stable intermediate state (prepreg). Thermostable layer bodies are produced from the prepregs obtained in subsequent processing steps.

The features of the invention are that epoxy resin, in particular having an epoxy equivalent of greater than 300, is mixed with polyisocyanates having a functionality greater than or equal to 2 in an isocyanate / epoxide equivalent ratio of 2: 1 to 10 t 1 and after application of this mixture is pre-crosslinked on a support or after impregnation of a structured support material with this mixture using a temperature of greater than 80 ⁰ O and that the pre-crosslinking of the resin system in the carrier material is carried out at temperatures between 130 18O ⁰ C within 2-5 min so that not more than 40 % of the reactive groups of the epoxides and the polyisocyanates are reacted and the resulting layered body under pressure and temperature in a known manner by complete crosslinking

of the resin system. »

The invention will be explained in more detail below using an exemplary embodiment.

Exemplary embodiment

The process according to the invention is illustrated by the following examples! ,

Example 11

80 parts by weight of a medium molecular weight epoxy resin based on bisphenol A having an epoxy equivalent of are dissolved in 100 parts by mass of toluene at a temperature of 60 ⁰ C * Hach obtained cooling to room temperature, a storage-stable resin-solvent mixture "Before the actual impregnation is this solution intensively mixed with 100 parts by weight of polymethylene polyphenyl isocyanate This impregnating solution has a gelation time of about 2 minutes at 16 ° C. This impregnating solution can be used to knead all known sheet-like reinforcing materials such as mica and asbestos paper, thermostable synthetic fiber fabrics and nonwovens, glass fiber fabrics and glass fiber webs, but also glass fiber rovings by thawing , knife coating or spraying are impregnated "In corresponding vertical or horizontal shafts drying the impregnated sheet-like structure at temperatures of 130 to 180 ⁰ C are 2 - 5 min dried" the result is a dry, tack-free Prepreg containing more than about 60 % reactive groups and then cut to size ·

Depending on the KLächengewicht the impregnated carrier "materials and the desired laminate thickness, a corresponding number of individual layers is stacked and specific pressure and a temperature of about 170 ⁰ C pressed in a press at a ₁ depending on the carrier material and the purpose of use *

After the pressure and the temperature have been maintained for approximately 20 minutes, the press can be cooled and the laminate removed from the press. In the case of a laminate with glass fiber reinforcement, flexural strengths of <5 \,> 300 N / mm can already be determined Loss factor tancHtiat but still a value of ca «25 · 10 ^ at room temperature · This value is improved to ca · 12 · 10 *" · ³ , if this laminate is at least two hours at 170 ⁰ C postcured »If the technological conditions allow the curing takes two hours in the press at 170 0 · This is achieved with the molding material such electrical and mechanical property values, which allow Λ to use such materials in machines and equipment which are intended for the heat resistance class F ·

Example 2;

80 parts by mass of a novolak Bpoxidharzes are dissolved at 6O ⁰ C in 100 parts by mass of acetone · After cooling this solution to room temperature gives a storage-stable resin-solvent mixture · Before the actual impregnation process of this solution is 100 parts by weight of polymethylene polyphenyl isocyanate is added and mixed thoroughly. With this impregnating the reinforcing materials mentioned in Example 1 can be impregnated · They are then dried in vertical or horizontal shafts dry at temperatures of 130 to 180 ⁰ C ca. 2-5 min · Bs produces a dry, tack-free prepreg by dipping, knife coating or spraying which can then be cut to desired formats ·

Depending on the basis weight of the reinforcing material used and the desired laminate thickness, a corresponding number of individual prepreg layers are stacked on top of one another and in a press at a pressure dependent on the field of application and the reinforcing material and on

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Temperature of about 170 ⁰ C pressed *

After two hours of pressure and temperature maintenance, the press can be cooled and the laminate removed from the press. ''>

Example 3:

Analogously to Example 1, wherein a brominated epoxy resin having an epoxy equivalent of 450 is used as the epoxy component. "After processing this resin solution according to the conditions mentioned in Example 1 or" 2, a thermostable composite is obtained which has the same properties as in Examples 1 and 2 has a significantly reduced flammability.

Claims (2)

- 7 claims for invention 1. A process for the production of laminates of high thermal stability using epoxy resins, characterized by » that epoxy resin, in particular having an epoxy equivalent of greater than 300, is mixed with polyisocyanates having a functionality of greater than or equal to 2 in an isocyanate / epoxide equivalent ratio of 2: 1 to 10: 1 and after application of this mixture to a support or after impregnation of a structured carrier material with this mixture using a temperature of greater than 80 ⁰ C is precrosslinked · 2 · procedure according to point 1,
characterized by that the precrosslinking of the resin system located in the carrier material is carried out at temperatures between 130 and 180 ⁰ C within 2-5 min so that not more than 40 % of the reactive groups of the epoxides and the polyisocyanates are reacted and the resulting layered body under pressure and temperature action are produced in a known manner by complete crosslinking of the resin system.