CS261111B1 - Process for preparing foam rubber - Google Patents

Abstract

The solution relates to a method of preparing foam rubber from natural or synthetic* rubber latex and waste foam rubber crumb. The essence of the solution lies in the fact that crushed waste foam rubber with a particle size given by a maximum dimension of 1.2 to 2.5 mm, preferably 1.25 to 1.6 mm, is dosed into the latex mixture in an amount of 1 to 50, preferably 5 to 15 parts by weight per 100 parts by weight of elastomers in the dry matter of the latex mixture. The crumb is homogeneously dispersed in the latex mixture, the mixture is mechanically foamed (whisked) and* vulcanized. This is followed by washing out unreacted residues of additives from the previous stages of the technology and drying the produced foam rubber. The main advantage of the method for preparing foam rubber according to the invention, in comparison with the known state of the art in this field, is the fact that the waste foam rubber crumb is processed here by a simpler and less energy- and economically demanding process than in the previously known processes.

Description

The invention relates to a process for the preparation of foam rubber from latex of natural or synthetic rubber and waste foam rubber pulp.

Foam rubber production produces two types of technological waste:

(a) unvulcanised waste - resulting from mold leaks or overfilling. This waste is not further processed due to its high content of liquid component, the evaporation of which adversely affects the processing economy. Mostly they are either incinerated or exported to landfills;

bj vulcanized waste - represented by overflows or scrap after vulcanization. Its processing and use is subject to drying and crushing. It is mostly used as a filling material for sound and thermal insulation.

Given the price (mostly foreign exchange) demands of the raw materials used, it is clear that producers are trying to minimize the generation of both types of waste mentioned above. It is known, for example, that the need for basic raw materials per volume (weight unit J) is related to the production method or equipment used. In this respect, the use of the Talalay production method is preferable to the Dulop method.

In the case of previously established production processes, the conversion to a new, more modern way represents a high conversion requirement. Therefore, this path is not always feasible for many. In practice, there is often a tendency to compensate for higher waste generation by better and more efficient recovery.

In one known method, for example, waste foam rubber is crushed to a particle size of 0.002 to 0.003 mra. Dispersion containing 47-50% dry matter is then formed with tall oil and added to the base latex mixture in an amount of 10% (dry matter per dry matter). According to the published results, the use of waste in the form described does not affect either the physical-mechanical values or the manufacturing process.

A further process is described in the literature in which the waste particles are mixed with 0.5-10% of the latex dispersion in an amount of 0.5-20% (dry). The treated waste particles are then mixed into the foam, gelatinized & vulcanized together. The foam obtained has good flexibility. In addition to the composition of the mixture used, no further details are known about this process.

Of interest may also be a process in which foam rubber wastes are treated by crushing and bonding the two-component polyurethane mixture without further heating. The blocks produced have a density of 120 to 200 kg / m ³ and are very regular in the structure. The amount of waste applied was not found in this process.

The main drawback of the above-cited principles of known waste foam rubber processing techniques is their great generality. In neither case is there a description of the technology that would make it possible to clearly assess the feasibility and convenience of the design. From this perspective, the following attempt to analyze the effects of these solutions cannot be considered to be entirely exhaustive. In the first cited solution, the disadvantage of disintegrating the waste foam rubber into very small particles is likely to be a disadvantage, which will obviously require special equipment and probably higher energy consumption. The latter solution mainly specifies the pretreatment of the waste foam rubber particles before adding them to the latex mixture. Obviously, the very inclusion of this adjustment complicates the technology as a whole, and the effectiveness of this operation cannot be assessed from the data available. The third procedure envisages the use of the polyurethane mixture as a binder and is therefore burdened with all generally valid problems associated with the application of polyurethanes. In addition to price considerations, these are at least hygienic and environmental impacts.

To a large extent, the process for preparing foam rubber from latex of natural or synthetic rubber and waste foam rubber pulp according to the invention contributes to eliminating the above drawbacks. The principle of the solution consists in that 1 to 50, preferably 5 to 15 wt. parts per 100 wt. % of the elastomers in the dry matter of the latex mixture, dosed the crushed waste foam rubber with a particle size given by a maximum dimension of 1.2 to 2.5 mm, preferably 1.25 to 1.6 mm. The pulp is dispersed homogeneously in the latex mixture, the mixture is mechanically foamed (whipped) and vulcanized. This is followed by scrubbing of unreacted additive residues from the previous stages of technology and drying of the foam rubber produced.

The treated foam rubber waste can be disintegrated advantageously in an undried state - i. has a dry matter content of 60 to 80 wt. percent.

The reason for processing the undried waste is to find out that the properties of this material are quite different from the dried ones. For example, the wet and dried specimens have approximately the same tensile strength values, but the ductility in a wet specimen is up to 100% higher and the compression resistance is about half (Table 1j. This is important for the next intended application.

Table 1

Properties of foam rubber before and after drying

PT (Ml’a} T (%)

P 86/2104 0.082 322

P 86 / 0403-3 0.096 164

The wet waste is crushed on a suitable mill type, for example a knife mill, a plate mill, etc. The particle size of the disintegrate is also important. In general, the coarser the ground waste, the less difficult it is to process and the worse the visual and organoleptic properties. It has been found that the particle size of the ground waste can range from 1 to 2.5 mm, preferably from 1.25 to 1.6 mm. The ground waste is easy to mix into the dispersion mixture and is virtually unrecognizable in the product. Also, the physical-mechanical values do not suffer harm.

The mixing of the disintegrate is carried out either in a container with constant stirring or dosing before or at the foam formation site. In the unfoamed mixture, the waste tends to partially float.

The foaming of the mixture is then carried out by conventional methods either intermittently by means of beaters or continuously in mixers (Eur-o-matic, OAKS mixer and the like).

Processing of whipped mixture is identical with the original technology, ie. filling molds, gelation prior to vulcanization, scrubbing of additive residues, especially surfactants, and drying. Excess foam during mold filling flows down, for example, onto a backing metal strip, which is introduced into a heated space where the adhering dripping cures, are removed and processed together with other overflows as described above.

The main advantage of the method of preparing foam according to the invention compared with the prior art in this field skutečPDT _(n) distasteful

3,73 7,76 wet

3,3 16,54 dry wears that the waste foam rubber pulp is processed here in a simpler and less energy intensive process than the previously known processes. In doing so, the waste is treated at the place of its generation by an economically advantageous process and all important paijameters of the final product are preserved. It is also important that a non-vulcanized portion of the waste is treated which is vulcanized together with the products and can then be treated in the same way as the vulcanized portion of the waste. Dispensing of waste into the »Latex mixture is in relation to the total amount of waste generated, giving the possibility to process virtually all waste generated and approaching the ideal without waste technology.

The following examples serve to illustrate the invention in greater detail:

Example 1

Foam rubber waste in the form of spills or drips was vulcanized concurrently with the filled mold in a vulcanization tunnel at 100 ° C in a steam environment for 20 minutes. After being removed from the backing sheet, it was crushed in a Condux plate mill; the moisture content was 71.12%.

Since the particle size of the ground foam rubber waste was too coarse for the application, it was ground on a knife mill and using a sieve with a 0 3 mm aperture. This achieved the particle size distribution of the disintegrate shown in Table 2.

Table 2

Sieve analysis of foam rubber disintegrate sieve size 0 (cm) 0,25 sieve drop (%) 97,5

The bulk density of the pulp (dry) was 123 kg / / m ³ .

Curing agents, zinc oxide, surfactants, sulfur, fillers and 5 wt.% Were then blended into the butadiene-styrene latex mixture (Polysar 2133). parts per 100 wt. parts of the elastomeric component in the dry matter of the latex mixture prepared waste scrap rubber (disintegrate). Everything was then whisked in a container with a laboratory beater together with the sodium hexaluminosilicate dispersion. After 2 minutes the mixture was foamed, filled into molds and pellet 0.2 0.18 0.125

83 66 was lowered at 110 ° C for 20 min. The vulcanized foam was then stripped of water residues of hexafluorosilicate and surfactants in water and subsequently dried at 60 ° C to constant temperature. moisture content.

The resulting physical-mechanical properties of the prepared foam rubber are shown in Table 3.

Example 2

The preparation of the mixture and the ingredients used were the same as in Example 1. The amount of crushed

61 7 waste byte but increased to 10, respectively. to T5 wt. parts. The mixing of the pulp took place without any problems in a very short time - within 2 minutes. Also the treatment - vulcanization, scrubbing and drying - was identical to Example 111

The quality of the porous structure and surface is free from obvious defects. The sample has no caverns or unrelated membranes.

The values of the physical-mechanical properties are given in Table 3.

T a b u 1 k and 3

Physical-mechanical properties of latex foam rubber without waste and containing 5, 10 and 15 wt. dFree waste properties per 100 wt. parts of the elastomeric component in the dry matter of the latex mixture.

a latex mixture of 5 wt. parts with 10 wt. parts with 15 wt. waste waste parts volume, weight (g / cm ³ ) 128.8 compression resistance (MPa) 0.016 tensile strength (MPa) 0.096 ductility (%) 164 permanent deformation (%) 3.70

134.7 137 149

0.015 0.014 0.017

0.106 0.1 0.113

168 176 196

3.19 2.52 3.66

Claims (2)

1. A process for the preparation of foam rubber from latex of natural or synthetic rubber and waste foam rubber pulp, characterized in that from 1 to 50, preferably from 5 to 15 parts by weight per 100 parts by weight of elastomer in the dry material of the latex mixture are added to the latex mixture. , dispenses crushed waste foam rubber with a particle size of a maximum size of 1.2 to 2.5 mm, preferably 1.25 to 1.6 mm, homogeneously in the inventive mixture, then the mixture is mechanically foamed and vulcanized, after which followed by scrubbing of the unreacted additive residues from the previous stages of technology and drying of the foam rubber produced. 2. Process according to claim 1, characterized in that the treated foam rubber waste is disintegrated and added to the ¹ latex mixture in an undried state and has a dry matter content of 60 to 80% by weight. Severography, n. Race 7, Most Price 2,40 Kčs