CS201764B1 - Method of biological waste water treatment - Google Patents

Abstract

The purpose of the solution is to remove slowly biodegradable substances from wastewater. The stated purpose is achieved by a method in which wastewater (1) is fed into a homogenization space (2), into which activated sludge is added from a biological treatment space (4), after which the entire content of the homogenization space (2) is fed into the biological treatment space (4), whereby the amount of activated sludge fed to the amount of organic substances in the wastewater fed into the homogenization space is in the ratio range of 1:2 to 1:20.

Description

The invention relates to a sintered polyolefin damping material based on a crosslinked copolymer of ethylene vinyl acetate in the form of vulcanized moldings with a specific weight of 0.078 to 0.122 grams per cubic centimeter and a hardness of 10 to 14 sh A, especially for sports purposes.

Sports equipment used by athletes in various sports, which may involve violent impacts on some of the more delicate parts of the body, is intended to provide protection against the consequences of these impacts, which are not only painful but can often result in serious injuries. This category of sports equipment includes helmets, but especially hockey gloves and elbow, knee, shin and shoulder protectors. In shaped parts, often leather, cavities are created that are sufficiently filled with a material capable of absorbing the kinetic energy of the impact. In the past, deer or goat hair was used for this purpose, later variously shaped parts or even handling scraps of foam materials. These designs introduce some impractical elements into the production process. Since filling the cavities is done by manually tamping the filling materials, it is a very lengthy operation. Moreover, the use of filler hairs is disadvantageous, both from a hygienic and functional point of view, because during use the filler becomes fatigued, which results in deformation of the protector and deterioration of its functional properties. Even filling the cavities of the protectors with growth plastic materials is not suitable /Czech patent No. 134 172; British patent 955 4θ6/, even if it is polyurethane foam materials, the reaction processes of which take place in situ /US patents 2 ^ύ 1 764

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2.90θ 943» 2.976 577; Canadian 851 652/, because precise non-dominance in the limited spaces of the cavities is difficult to control. The materials used for direct bonding to shaped parts of sports equipment are usually heavy or weak, and the high specific gravity of the shock-absorbing materials is often their fundamental disadvantage, because protective sports equipment should provide maximum protection at minimum weight so as not to reduce or limit the sports performance of the athlete.

The material with these properties is a lightweight polyolefin damping material based on a crosslinked ethylene-vinyl acetate copolymer in the form of vulcanized moldings according to the invention, the essential feature of which is that this material, with a content of 65 to 85 parts by weight of a copolymer of ethylene with vinyl acetate, in which the content of bound vinyl acetate is 5 to 25 percent by weight, 20 to 30 parts by weight of natural or polyisoprene synthetic rubber,

1.8 to 2.1 parts by weight of zinc white, 0.9 to 1.1 parts by weight of stearin, 2 to 3 parts by weight of 1,3-bis(dialkylperoxide)benzene, 4.5 to 6 parts by weight of azodicarbonamide, 1.2 to 1.8 parts by weight of dinitrosopentamethylenetetramine and 10 to 20 parts by weight of precipitated calcium carbonate has a specific gravity of 0.078 to 0.122 grams per cubic centimeter and a hardness of 10 to 14 Sh A.

The technical effect of the lightened polyolefin damping material for sports purposes according to the invention lies in improved lightness and elasticity, while maintaining excellent damping properties, which is a consequence of the lightened and crosslinked base material, an ethylene vinyl acetate copolymer with a bound vinyl acetate content of 5 to 25 percent by weight. The increased lightness is given by a specific gravity in the range of 0.078 to 0.122 g/m^ and results from the use of a combination of two blowing agents, namely azodicarbonamide and dinitrosopentamethylenetetramine, the function of which will be described later.

The expanded polyolefin damping material according to the invention with the above-mentioned properties is prepared by kneading on a calender or in a kneader, in the first case for about 24 minutes at a roller temperature of about 100 °C, in the second case for about 14 minutes at a rotor and casing temperature of the kneading device of about 110 to 120 °C. The mixing is continued until a homogeneous mass is obtained, which is then drawn into films, from which preforms are cut. These are then vulcanized, for example, in stack presses into plates at a temperature of 168 to 172 °C under a pressure of 20 MPa and after approximately twenty-four hours of stabilization, they are ready for use in sports equipment.

After re-extrusion, up to 15% of waste generated during the handling of pressed boards can be added to the expanded polyolefin damping material according to the invention. The physical-mechanical values of the damping material according to the invention are as follows:

Specific gravity 0.078 to 0.122 g/cm^

Hardness 10 to 14 Sh A p

Tensile strength at least 7.0 kp/om

Elongation at least 150%

Tear resistance at least 4.0 kp/om

Rebound elasticity of at least 40%

Permanent deformation maximum 50%

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Achieving a specific gravity in the range of 0.078 to 0.122 g^cm ³ for the expanded polyolefin damping material according to the invention is a very demanding and unusual phenomenon, especially from the point of view of the production process of pressing. This specific gravity is achieved by expanding the material after the reinforcement period has ended and after releasing the pressure on the stack press and thus on the body into which the material is enclosed during the reinforcement. After releasing the pressure, the material actually shoots out of the molds and expands to a volume that is influenced both by the structural properties of the material phase, but especially by the type and amount of blowing agent used. The combination of ethylene vinyl acetate with natural rubber guarantees good structural properties and to achieve the specified specific gravity, azodicarbonamide is used as the basic type of blowing agent, mainly because the crosslinking of the material takes place at higher temperatures, from 170 to 175 °C, and the decomposition of the azodicarbonamide blowing agent itself does not occur earlier at lower temperatures. However, this blowing agent develops a significant amount of gas, which is why the expansion of the material is too rapid and, despite the excellent properties of the basic base, defects in the appearance of the pressed plates cannot be avoided, especially in the edges of the plates, which are torn.

Therefore, to achieve the specified specific gravity under possible processing conditions, especially during pressing, and especially when releasing the plates from the press, it is advantageous to use dinitrosopentamethylenetetramine as the second blowing agent, which creates larger pores than azodicarbonamide and its activity is slightly lower. The advantage of this combination is that the amount of the basic blowing agent is actually reduced. As a result of the combination of the formed pores, the expanded polyolefin damping material according to the invention is better processed into the desired plates and thus the necessary very low value of the specific gravity is also achieved and in this way the expanded material according to the invention actually acquires its basic and excellent properties.

Example 1

A compounded polyolefin cushioning material was produced using the procedure described in the previous description, which was used for sports equipment protectors, for the production of orthopedic aids and for shoe inserts. The basic mixture of this material used, expressed in weight percentages;

Ethylene vinyl acetate with 12% vinyl acetate content 58

Polyisoprene synthetic rubber 20

Zinc white 1.6

Stearic acid 0.8

1,3-bis/dialkyl peroxide/benzene 1,7

Azodicarbonamide 4

Dinitrospentamethylenetetramine 1,2

Calcium carbonate 12

Pigments 0.7

Tensile strength

The produced expanded polyolefin damping material according to the invention exhibited physical values!

Hardness Sh A 14

0.7

MPa

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Ductility % 180 Tear resistance N/om 45 Permanent deformation % 35 Elasticity % 45 Dimensional weight g/m^ 0.09

Example 2

For the production of shock-absorbing mattresses, a lightweight polyolefin shock-absorbing material was produced, which contained in weight percentages:

Ethylene vinyl acetate with 12% wool acetate content 50 Natural rubber, softened 24 Zinc oxide 2.1 Stearic acid 0.9 1,3“bis/dialkyl peroxide/benzene 2.0 Azodicarbonamide 3.1 Dinitrospentamethylenetetramine. 2.1 Calcium carbonate 15 Pigments 0.8 Physical-mechanical values: Hardness Sh A 12 Tensile strength MPa 0.65 Ductility % 200 Tear resistance N/om 48 Elasticity % 38 Permanent deformation % 42 Density g/oa? 0.11

SUBJECT OF THE INVENTION

Claims (1)

Cellular polyolefin cushioning compound based on vulcanized molded ethylene vinyl acetate copolymers having a density of 0.078 to 0.122 grams per cubic centimeter and a hardness of 10 to 14 sh A, in particular for sports purposes, characterized in that it consists of 65 to 85 parts by weight of ethylene copolymer e vinyl acetate, wherein the bound vinyl acetate content is 5 to 25% by weight, 20 to 30 parts by weight of natural or polyisopran eynthetic rubber, 1.8 to 2.2 parts by weight of zinc white, 0.9 to 1.1 parts by weight of stearin, 3 parts by weight of 1,3-bis (dialkylperoxide) benzene, 4.5 to 6 parts by weight of azodicarbanamide, 1.2 to 1.8 parts by weight of dinitrosopentamethylenetetramine and 10 to 20 parts by weight of precipitated calcium carbonate.