SU844360A1 - Extrusion head for applying polymeric coatings onto articles - Google Patents

Description

one

This invention relates to a technology for the manufacture of polymer products and coatings used in mechanical engineering and other industries.

A known extrusion head for applying polymeric coatings on fibers, comprising a housing with a melt feed inlet, a mouthpiece, a mandrel, the mouthpiece being made in the form of two plates equipped with partition walls 1.

The change in the amount of applied polymer in a known head is regulated by changing the width of the gap between the mouthpiece plates and the mandrel with the help of an adjustment, and their elements — screws.

A disadvantage of the known head is considerable wear and tear of the adjustable, nx elements and limited use due to the possibility of coating only the fibers.

The least technical essence of the invention is an extrusion head for applying polymer coatings on products, comprising a body made in the form of a series of sections with dividing walls between them forming outlet openings for polymer 2.

The latter extrusion die ensures that the polymer coating is applied only to flat products in the form of individual strips. The disadvantage of this extrusion head is that it does not allow to obtain coatings of variable thickness on products of a complex curvilinear profile. The presence of joints, the lack of a smooth transition between the individual bands of polymeric material reduces the quality of the coating. The purpose of the invention is to expand the technological capabilities of the extrusion head by providing the application of coatings of variable thickness on the products of a curvilinear profile.

The goal is achieved; the fact that in the extrusion head for applying polymeric coatings on products comprising a body made in the form of a series of sections with dividing walls between

by them forming polymer outlets for the invention according to the invention, each section is provided with adjustable heaters installed on its inlet section, the outlet end of the body is made along the profile of the forming product, and the thickness of the dividing walls does not exceed the product of the half sum of the width of the adjacent outlet holes polymer ki during extrusion.

FIG. 1 shows an extrusion head, a general view; in fig. 2 - section A-A of FIG. one; in fig. 3 - extrusion head connected to the injection molding machine.

The extrusion head for applying polymeric coatings comprises a housing 1, made in the form of a row of section 2 with separation walls 3 between them, forming polymer outlet openings 4 that expand towards the polymer exit. At the entrance section of each section 2, adjustable heaters 5 with thermal insulation 6 are installed. The thickness of the separation walls 3 does not exceed the product of the half amount of the width of the outlet openings 4 by the coefficient of polymer extrusion.

The choice of wall thickness between adjacent head outlet openings is based on the following factors.

In the process of extrusion of a polymer, its dimensions become larger than the sizes of the outlet openings of the head due to the highly elastic recovery of the polymer, which is characterized by the polymer stretching ratio K.

The polymer extrusion ratio is determined experimentally and is known for various types of polymers, in particular for phenol-rubber compositions, this ratio is 4-5%.

Assume that the material is extruded evenly on both sides of the head outlet sections, then one side of the actual material will be ti

  or ETC.,

where ti, tz is the amount of stretching of the material of adjacent jets, mm; l / 2-sizes of outlet openings

adjacent sections, mm; K is the coefficient of stretching of the material during extrusion. The total amount of stretching of the material of adjacent jets will be

i f, + {, lJ2K (l, + l,).

Therefore, to ensure the fusion of individual jets after the material has entered the monolithic flow, the thickness of the separation walls should be no more than t.

For example, when extruding phenol-rubber compositions (K 4: -5%) with the width of the openings of the adjacent sections / 1 150 mm and mm, the maximum wall thickness will be (150 + 50) 5 mm.

However, in order to obtain a qualitative connection of individual jets into a monolithic flow, it is necessary that the jets at the junction should be under some pressure, facilitating their mutual penetration. Experimentally established that the optimal thickness of the separation wall

(or its lower limit) is 0.6-0.8 of its maximum value (in our case, an experience of 3-4 mm).

The drive 7 of the head is designed to rotate the part to be coated, and the mechanism 8 provides for the reciprocating movement of the part in the vertical direction. The extrusion head is connected to the injection molding machine 9. The output end of the extrusion head is made according to the profile of the generator (FIG. 3).

The coating process with an extrusion die is carried out as follows.

The body 1 of the extrusion head is installed along a forming part 10, which is attached to the rotation from the drive 7. The part 10 together with the drive 7 has a reciprocating movement in the vertical direction from the mechanism 8 to easily remove and fix the part 10. The polymer comes from the injection molding machine 9 and is distributed over separate sections of the 2 heads, in which a controlled temperature of the extruded mass is maintained by means of adjustable heaters 5, which determines the viscosity of the applied polymer and, accordingly, , The volume of its output. In particular, for phenolic rubber polymer compositions, the temperature of the mass varies from 80 to 120 ° C, the volume yield of the polymer can be adjusted 4-5 times. Since the head consists of separate sections 2 with independent adjustable heaters 5 in the upper part, volumetric polymer output is provided individually in each of them and polymer leakage over the cross section of the extrusion head body 1 is excluded.

When the polymer leaves the head, due to the presence of expanding outlets 4 with dividing walls between them, not more than the product of half the amount of the bold outlets 4 by the polymer stretching ratio during extrusion, individual jets of material merge into a single monolithic stream and cover the entire surface of the rotating part 10 After coating, it is calibrated and cured by known methods.

The proposed head provides an increase in the productivity of the process of applying a polymer coating of variable thickness. This is achieved in that the coating is applied in a wide strip covering the entire surface forming the part. The absence of joints, the smooth transition between areas of different thickness improves the quality of coatings.

Claims (2)

1. USSR author's certificate JMb 512927, cl. In 29F 3/04, 1974. 2. USSR author's certificate number 413053, cl. In 29D 7/04, 1972 (prototype).