CS234254B1 - Reinforcing tempering layer for molds for plastics - Google Patents

Abstract

Reinforcing tempering layer of molds intended especially for injection molding of reinforced thermosets and consisting of a galvanoplastic shell, under which is placed a reinforcing layer consisting of a tempering layer with built-in heating or cooling elements and an insulating layer. The reinforcing tempering layer consists of a mixture of epoxy resin and filler in a ratio of 1 : 3 to 1 : 9 parts by weight, the filler consisting of 50 to 100% by weight of metal bodies and not more than 50% by weight of dried silica sand.

Description

The invention relates to a reinforcing tempering layer of plastics molds, e.g. molds for injection molding or molding of reinforced thermosetting plastics, the functional layer of which is mainly made of a galvanoplastic shell.

Galvanoplastic shells, used as functional layers in molds for injection molding or molding of plastics, reinforced plastic products or sheet metal drawing, need to be reinforced or supported from the rear, since at a relatively small wall thickness of the shell ranging from 5 to 10 mm in most cases, allow for its self-support. The reinforcement is usually performed by embedding with metals or resins. Metal embedding is carried out at high temperatures, which often causes deformation of the heated shell. In addition, the casting metal, which may only be heated to the melting point with respect to the shell, usually does not flow sufficiently into the corners and depressions of the back of the shell so that bubbles remain therein and the shell is not evenly supported. The casting metal is also very difficult to connect with the metal of the shell and the built-in heating or cooling elements. As a result of the compressive stress, gaps may form between the casting metal and the shell. Also different coefficients of thermal expansion of the casting metal and the shell cause operational problems. The mechanical properties of the shell are adversely affected by the heat shock caused by the high temperature of the embedding metal. Sometimes, therefore, shells in the mold are encapsulated with resins, which again usually results in considerable pressure stress. In molds there is a creep of the casting material, the reinforcing resins acting as a hydraulic medium. The thermal conductivity of said materials is also very low, which causes considerable technological problems in tempered molds.

These deficiencies are largely overcome by the reinforcing tempering layer according to the invention. The tempering layer is determined

- 2,234,254 for molds for plastics molding, eg for injection molding or molding, for example, · thermosetting plastics · Such mold consists of a galvanoplastic shell under which a reinforcing layer consisting of a reinforcing tempering layer with built-in heating or cooling elements and a reinforcing insulating layer is deposited characterized in that the reinforcing tempering layer consists of a mixture of epoxy resin and filler in a ratio of 1: 3 to 1: 9 parts by weight. The filler comprises a mixture of 50 to 100% by weight of metal bodies with at most 50% by weight of dried silica sand.

The form in which the reinforcing tempering layer according to the invention is used brings numerous advantages in practice. Since the potting is carried out at normal temperatures, the shell does not deform or its mechanical properties are impaired. The heating or cooling elements can be arranged on the back of the shell and then embedded with a filled epoxy resin forming a reinforcing tempering layer. Due to the high content of fillers, it reinforces the perfectly galvanoplastic shell over its entire surface and at the same time distributes the tempering medium well. The second insulating layer can be applied immediately after the tempering layer has set. Another advantage is the possibility of continuous initial heating and subsequent cooling of the mold according to the requirements of the production mode. The tempering layer quickly dissipates heat from the surface and the mold can be cooled as required. The above-mentioned advantages of the tempering layer are particularly evident in the production of laminate panels with surface gelcoats, in which the quality layers cannot be applied to an overly warm mold, because the styrene evaporates rapidly from the yet unpolymerized spray layer and the gelcoats do not have the required parameters. In line production, however, especially in the case of smaller parts, there is a very fast working cycle, which can be up to 30 minutes per part, and thus the mold can be heated up to 50 ° C or more due to exothermic temperatures.

The use of the reinforcing tempering layer according to the invention is described in more detail in the following examples.

Example 1

Foirnia for injection molding of reinforced thermosetting plastics consists of a galvanoplastic shell, the inner side of which is

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- 3 anchoring elements · Under the galvanoplastic shell there is a reinforcing layer of the mold consisting of a tempering layer with built-in heating elements and another reinforcing insulation layer. The reinforcing tempering layer is made of a mixture of 25 parts of low molecular weight epoxy resin and 75 parts of a 1: 2 mixture of cast iron and aluminum sawdust. The reinforcing insulating layer is made of a mixture of quartz sands and epoxy low molecular weight resin in a 9: 1 ratio.

Example 2

The same form as in Example 1 is provided with a reinforcing tempering layer consisting of a 10: 90 mixture of low molecular weight epoxy resin and filler, the filler consisting of 90% by weight. % of iron filings mixed with 10 wt. of dried silica sand.

It is also advantageous to use copper filings or bodies, aluminum or copper rivets, chopped wires, metal chips and the like as epoxy resin fillers.

The tempering layer according to the invention is also suitable for other types of molds, for example molds with a laminate functional layer.

Claims (1)

Reinforcing tempering layer of molds for molding plastics eg for injection molding or pressing of eg thermosetting plastics, molds consisting of a galvanoplastic shell, under which a reinforcing layer consisting of said tempering layer with built-in heating or cooling elements and an insulating layer is placed, tempering layer characterized by % of a mixture of epoxy resin and filler in a ratio of from 1 to 3 to 1: 9 parts by weight, the filler consisting of 50 to 100% by weight of metal bodies and at most 50% by weight of dried silica sand.