SU1722857A1 - Method for making hollow articles from thermoplastic materials - Google Patents

Abstract

Use: for pneumatic and vacuum molding of complex profile single or multi-layer products of closed and open type, mainly from thermoplastic materials. SUMMARY OF THE INVENTION: Prior to blow molding, preforms are formed from layers of bulk material separated around the perimeter with an anti-adhesive layer by pressing them when heated to the melting point of the material, followed by cooling the blanks to the temperature of forming the product. Then, the billet, heated to the molding temperature and connected along the perimeter, is blow molded by applying air between them under pressure and vacuuming the mold cavity on both sides of the billet. 3 il.

Description

The invention relates to the manufacture of hollow articles from thermoplastic materials by blowing flat blanks heated to the molding temperature.

A known method of manufacturing hollow articles by blow molding flat blanks from thermoplastic materials includes preliminary production of a flat blank by extrusion or injection molding, heating of the blank, closing it in the mold with subsequent air supply and blow molding.

The disadvantages of this method are the complexity of the instrumentation process, limited technological capabilities, especially when receiving large-sized products of complex configuration.

There is also known a method of making hollow articles from thermoplastic materials by blow molding flat blanks heated to the molding temperature and connected around the perimeter by applying air pressure between the blanks under pressure and evacuating the mold cavity on both sides of the blank.

The disadvantages of this method are that it does not guarantee the density of the weld around the perimeter of the blanks, which does not ensure the integrity of the cavity between them, and therefore reduces the quality of the products; the use of previously obtained thermoplastic flat blanks does not allow to obtain products with desired physical and mechanical properties, which also reduces their quality and limits technological capabilities, besides requires special equipment for the production of flat blanks and

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additional space for their storage, which increases the complexity and power consumption of production.

The purpose of the invention is to improve the quality of products, reduce energy costs and expand technological capabilities.

The goal is achieved by the method of making hollow articles from thermoplastic materials by blow molding flat billets heated to the molding temperature and connected along the perimeter by applying air under pressure between the blanks and evacuating the mold cavity on both sides of the blanks molded from layers of bulk material, separated by an anti-adhesive layer, by pressing them when heated to the melting temperature of the material, followed by cooling ovok to molding temperature of the article.

FIG. 1 shows the loading position; in fig. 2 - the same, forming the blank; in fig. 3 - the same, molding the product, as well as a specific example of the method.

A loose thermoplastic material, for example polyethylene grade 273-79 GOST 16338-85, is loaded into a frame 2 mounted on platform 1, made to the size of the blank, in granular form in an amount necessary to form the bottom layer of the blank. Then, a layer of a slightly smaller bulk layer, for example a film of cellulose triacetate, is placed on the lower layer of the preform to the thermoplastic material.

Bulk, sheet and gel-like materials can also be used as anti-adhesive interlayers.

The interlayer is filled with the necessary amount of thermoplastic material to form the upper layer of the preform. At the same time, the number of anti-adhesive interlayers depends on the number of layers of thermoplastic material.

The blank thus formed, together with platform 1, is fed into the working zone of the press 3, where it is placed under pressure between the heated plates 4 and 5. At the same time, the air in the bulk layers is sucked out by suction, thereby achieving flat pieces of the product without air bubbles.

The billet is heated to the melting temperature of the thermoplastic material and held at this temperature until the lower and upper layers are completely melted around the perimeter of the billet (where there is no anti-adhesion layer). In this case, a tight hermetic cavity is formed between the layers of the preform, and the presence of an adhesive layer between the layers of the thermoplastic material completely excludes the possibility of their sticking together in other places. Then the heating is stopped, a cooling medium is supplied. Pressed

0, the billet is cooled to the molding temperature of the product, after which the mold 6 is fed under the flat billet, which is pressed by the working body of the press 3 to the billet held by vacuum on the plate 4.

5 As the mold 6 is inserted into the workpiece, material is compacted around the perimeter of the mold closure with the workpiece. At the same time, in order to avoid cutting the workpiece with the mold, special stops are provided on the latter, which provide for the regulation of the depth of the mold's introduction into the workpiece.

After the mold 6 is closed with the blank, the blank holding vacuum is removed, and air is fed under pressure through a needle or nipple into the blank cavity. In doing so, the preform is inflated, repeating the shape configuration of the product. At the same time, a mold cavity is evacuated on both sides of the workpiece.

. Upon completion of the molding of the product by blowing flat blanks, the pressure of the press 3 is released and the mold 6 is moved to the unloading position of the finished product,

5, in particular, the cab of the tractor cabin 70B-5712011-11, and in its place frame 2 is fed with a molded blank of bulk layers of thermoplastic material separated by an anti-adhesive layer, installed on platform 1, and the technological cycle is repeated.

The proposed method, in comparison with the known method, provides an increase in the quality of products by creating a guarantee of the tightness of the weld seam, obtaining flat blanks with desired physical and mechanical properties; reduction of energy consumption and labor intensity in the manufacture of the product except

It is necessary to preliminarily obtain flat blanks and to multiply them. heating in the preforming process, the method extends the technological capabilities through the use of

5 wide range of thermoplastic materials in the form of primary raw materials (powder, granules), and in the form of waste products (chips, crushed), the formation of flat blanks from layers of various thermoplastic materials, as well as

the possibility of obtaining multilayer products of closed and open type; allows to produce different-thickness flat blanks to compensate for wall thinning during the molding of products of variable cross-section of a complex configuration; the need for special equipment for the pre-production of flat blanks, as well as the availability of production space for their storage, is eliminated.

Claims (1)

The invention of the method of manufacturing hollow articles from thermoplastic materials by blow molding flat blanks heated to the molding temperature and connected around the perimeter by applying air pressure between the blanks under pressure and evacuating the mold cavity on both sides of the blank, reducing energy consumption and expanding technological capabilities, before forming blanks are formed by blowing from layers of bulk material, separated by an anti-adhesive layer, by pressing them when heated to the melting temperature of the material, followed by cooling the blanks to the molding temperature of the product. . & / .. 25 3d