CS210317B1 - Method of inserting the admixtures in the polymeres - Google Patents

Abstract

The incorporation of additives into thermoplastic polymers, in particular to give foamable polymers, which are used for the preparation of an extrudable melt is carried out without the use of an adhesion promoter by adsorbing the additives onto foam flakes, optionally mixed with polymer granules, and adding them in this form to the thermoplastics before the melting. The uniform distribution of the additives enables the preparation of end products having a smooth surface without bubbles or holes. Blockage of the extruder due to precipitated additives is also prevented.

Description

(54) Method of incorporating additives into polymers

AND

The invention relates to a process for incorporating additives into polymers, in particular into a foamable polymer.

It is known that the components according to the recipe are mixed in a mixer for the production of finely powdered foams and then fed to the extruder via a metering device.

The components according to the recipe form the basic material, nucleating agents and other additives. For the production of foams, auxiliaries in the form of additives with small grain sizes are used; in the fraction range up to 200. The nucleating agents dyes and other additives are applied to the polymer granulate in a mixer and distributed as best as possible on the surface of the polymers. If the addition of pulverulent excipients and additives exceeds the granulation capacity of the granulate, which is determined by the properties of the components to be exchanged, in particular the adhesion forces between the polymers and the additives, there is a risk that the additives are partially separated from the granulate.

It is known that citric acid and sodium bicarbonate are used as nucleating agents for the production of foams. However, it is known that these nucleating agents are added in amounts such that the reaction of the acid with the carbonate produces about 0.1 to 5 parts by weight of carbon dioxide per 100 parts by weight of the polymer and blowing agents used. .

A small excess of the carbon dioxide generating agent is known to be used to prevent the free effect of the free acid on the extruder material. The known ratio numbers and components are between one portion of citric acid to one portion of bicarbonate and one portion of citric acid to a maximum of two portions of sodium bicarbonate, and the absolute portions used may be different.

The effect of the nuclear agent is dependent on the nature of the thermoplastic to be strengthened. The relatively small variations in the nucleating agent system used may have a decisive effect on the cell size of the foam hmooy. Thus, it was during the foaming polystyrene found to be at the wilderness acid hydrate 'citrnnové and anhydrous citric acid to obtain a finer cell structure than in the general poi ^ APPLICATION anhydrous citric acid, or a hydrate kyseMny C intron-Adhesion thienylsulfonyl MEEI these substrates, ^and t ^γ and plastic granulate are relatively small. Therefore, part of the citric acid and sodium bicarbonate deposited on the granulate is separated when the mixture is conveyed. Separated components according to the recipe are deposited in conveyor and feeder systems.

Kysee's lemon absorbs moisture from the ambient air and reacts in part with sodium bicarbonate. In this case, lumpy aglomeeate forms. From time to time, some of these products are torn off by the transport stream and reach the extruder. The performance of the humogified extruder generally is not sufficient to distribute the relatively hard agglomerates and to distribute them in the plastic. These solidify in the extruder under the effect of elevated temperature and lead to clogging of the nozzles as well as holes and defects in the foam. According to the invention, the two substances, when dispensed, of the mixture into the extruder fall away from the polymer granulate and lead to clogging of the extruder screw. Incrustations from time to time are separated from the extruder screw, clogging the nozzles, and lead to the formation of holes in the foam at the same time. Due to the loss of the active agent during transport, melting of the polymer at the exit of the nozzle does not give the necessary nucleating agent concentration. For this reason, the formation of the fine foam structure is greatly affected. The foam obtained is large porous and its structure is enhumoogeele.

For many purposes, such a foam is enriched.

The Moonnst enhancement of the granulating ability of the granulate with respect to the nucleating agent consists in the addition of adhesives. However, when the adhesive composition is required to bind the total amount of nucleating agent, the formation of the foam structure is influenced and the quality of the foam is reduced.

Another known possibility to improve the homouenity of the distribution of the nuclear agent in the plastic composition is the difficulty of the masterbatch of the nuclear agent.

Processing difficulties may occur in the preparation of the masterbatch, since the flow temperature of the polymer is more than the decomposition temperature of the emulsion component.

Therefore, when incorporating the eukeleliness of the composition, the effect as a pore regulator can be. Secondly, the additional step of processing the masterbatch increases the cost of producing the foam.

In the known systems of the three component formulation, it is disadvantageous to ensure uniform and constant dosing of the mono-active substances. In the case of uneven dosing of the individual components or the composition of the dosed nucleating agent to be varied, the foam structure is uneven and in many cases has coarse cells. However, for the bulk of the reports of thickened foams, a material having a uniform and fine foam structure is required.

Analogous problems arise in the incorporation of additives in the foamable thermoplastics.

When foaming polyethylene, ethylene polymers, as well as mixtures composed of polyethylene and these polymers, the disadvantage is that, especially when adding certain pigments, the foam structure is relatively coarse.

A known method, for example for dyeing thermoplastics, consists in applying the color pigments to the plastic material in a simple mixer, for example a drum mixer, a rotary mixer or a two-conical mixer.

The color pigments adhere to the granulate on the basis of the adhesive forces occurring between them. In this way, however, only small amounts of pigment can be bonded to the granulate, and there is also a risk that some of the pigment will fall off the granulate when the mixture is conveyed to the processing machine, thereby affecting the color tone of the resulting end product. Slightly larger pigment particles require the addition of adhesives. In order not to adversely affect the properties of thermoplastics, only small amounts of adhesive agents can often be used.

Also in this mode of operation, the proportion of pigment that can be applied to the granulate is still relatively small. With a larger pigment addition, lumps are easily formed. In order to homogeneously incorporate larger amounts of pigment into the thermoplastic, mixing is carried out on a kneading machine according to one known method. Such production of a color blend constitutes an additional working process for which a very expensive mixing device such as a kneading machine, a kneader, etc. is necessary. The same applies to the incorporation of other additives.

The purpose of the invention is to improve the homogeneous distribution of additives in the plastic melt and to increase the formation of fine foam cells.

SUMMARY OF THE INVENTION It is an object of the present invention to apply additives required for processing plastics in a simple mixer, without the use of adhesives, to polymers such that the concentration of the mixture does not change substantially when conveyed from the mixer to the extruder. in constant concentration, or the effect of additives on the molded material is the same in quality and quantity.

This object is achieved by a process for incorporating additives into polymers in which a mixture consisting of one or more thermoplastics with the necessary additives is heated to a temperature sufficient to melt it, or a blowing agent is introduced into the melt, which is homogenized therewith; The temperature at which it is optionally extrudable as a foam according to the invention is that the additives are adsorbed onto a polyrene, flake matrix of polyethylene or a mixture composed of a copolymer of polyethylene and ethylene, or a mixture of a polyrene flake matrix and a polymer granulate having specific gravity up to 0.6 g / cm @ 2, open cell fraction of 50 to 95% and the same or different composition of polymers than the parent polymer.

Preferably, citric acid and carbonate are used as additives, wherein 1.5 to 15 moles, preferably 2 to 6 moles of bicarbonate or 0.8 to 7.5 moles, preferably 1 to 3 moles are adsorbed per weight equivalent of organic acid. carbonate.

The thermoplastics used are preferably polyethylene, high or low density, polypropylene, polyamide, polyvinyl chloride, polystyrene, as well as copolymers and graft polymers of ethylene, propylene, vinyl chloride, styrene with other monitors such as vinyl acetate, vinyl propionate and ethylene; propylene with vinyl chloride and _? optionally or mixtures thereof.

It is also advantageous to use mixtures of these thermoplastics with waxes, such as polyethylene waxes, optionally their anoxidates and / or rubber.

Blowing agents are readily volatile organic substances such as butane, heptane, fluorocarbon, chlorinated hydrocarbons or mixtures thereof, and / or solid organic or inorganic substances, namely mixtures of mono- or dibasic organic acids with carbonates of a series of alkali or alkaline earth metals. Preferably, 1.5 to 15 moles, preferably 2 to 6 moles of bicarbonate or 0.8 to 7.5 moles, preferably 1 to 3 moles of carbonate are used per equivalent of the weight of the organic acid.

As additives, nucleating agents, solid blowing agents, colorants, flame retardants, stabilizers, fillers, antistatic agents, reinforcing materials, glidants or fungicide are used.

The additives are applied to the polymeric flake matrix by means of a rapid mixer, a pump mixer, a rotary mixer or a double-cone mixer. Due to the large specific surface area of the foam flakes, the additives adhere well and do not fall off during transport. The ratio of the foam flake / additive mixture is between 0.5 and 200 parts by weight of foam flakes per 1 part by weight of ingredients, preferably between 10 and 100 parts by weight of foam flakes per 1 part by weight of ingredients.

The necessary mixing times depend on the carrier and formulation used and range from 0.25 to 60 minutes. According to the process of the invention, the additives are fed in a uniform amount into the polymer. There is no loss during transport, the additives in the machine parts are prevented. In particular, the produced foams have a uniform surface, no holes and bubbles are formed.

The invention will be explained in more detail below with reference to exemplary embodiments.

Example A 1 mm thick polyethylene foam sheet with a specific gravity of 0.15 g / cnP was crushed in a flake crusher. The foam flakes had a bulk density of 0.07 g / cm 2.

kg of foam flakes were mixed in a pump mixer with 225 g of citric acid and 225 g of sodium bicarbonate. Stirring time was 30 minutes. The mixture was fed through a weighing scale into a twin-screw extruder. It was also dosed into the feed funnel of the polyethylene extruder via a second dosing weight.

5 kg of the mixture was dosed per 50 kg of polyethylene granulate. Plasticization was carried out at temperatures of 165 ° C and in the region of relative pressure reduction, a 4% by weight mixture of trichloronofluoromethane and dichlorodifluoromethane in a ratio of 1: 4 was injected through the inlet port. In the following extruder regions, a blowing agent has been incorporated into the plastic melt. The melt temperature of the plastic has decreased. For better homogenization, the plastic melt was transported through a single-screw extension to a molding head equipped with an annular nozzle. At the plastic melt outlet of the extruder, the material foamed under the effect of the incorporated blowing agent.

A tubular film was formed which was drawn through a cooling pear. The cooling effect of the cooling pear, as well as the air blown into the hose and the cooling air blown onto the hose foil from outside, fixed the foam structure. The hose foil was cut, expanded, cooled by cooling air passage and wound up. characterized by foam cell uniformity, pore diameter from

0.001 to 0.5 µm and an average number of pores of 50 per mm. The open cell fraction of the surface of the foam flakes was 50. The film showed no formation of holes and bubbles and had a closed surface.

After 5 tons through, there were no deposits on the dosing organs and the auger.

If the nucleating agent was applied as usual to the granulate and in this form dispensed into an extruder, these foamed films had the following properties:

The diameter of the pores ranged from 0.1 to 1.0 mm, the average number of pores being per mm * ´. The surface was not completely closed. After passing 20 kg of the mixture, it was deposited in the transport routes over 100 g of nucleating agent. After 5 tons through, deposits in the Snail appeared.

EXAMPLE 2 mm thick polyethylene foam sheet having a density of 0.15 g / cm ^ vd was crushed into flakes -tiči ^y. The foam flakes had a bulk density of ^0.07 g / cm 2. 15 kg per ^{liter of} foam were mixed in a pump mixer with 120 g of citric acid and 360 g of sodium bicarbonate. The mixing time was 30 minutes. The mixture was fed through a weighing scale into a twin-screw extruder. A polyethylene granulate was also metered into the feed funnel of the extruder via a second dosing weight.

5 kg of the mixture was dosed per 50 kg of polyethylene granulate. The plasticization was carried out at temperatures from 165 ° C and in the area of relative pressure reduction, a 4% w / w mixture of trichloro-monofluoromethane and di-diphenyl difluoromethane was injected through the inlet throat in a ratio of 1: 4. In the following extruder regions, a blowing agent has been incorporated into the plastic melt. The melt temperature of the plastic has decreased. For better performance, the plastic melt was conveyed via a single-extension to a molding head which was provided with an annular nozzle.

At the melt outlet of the plastic from the extruder, the material foamed under the effect of the incorporated blowing agent. A tubular film was formed which was drawn over the cooling pear. Cooling. the foam structure was fixed by the action of a cooling pear and a throat in the exhaust air hose and externally on the blowing cooling air hose film. After the fixation with a knife, the tubular foil was cut, expanded, cooled by cooling air and wound. Obtained after about 2 ^p vinegar pore oe ^{s e} c o and ^{15 mm2. S} hare otevřenýcli BuO ^Ek ovrc ^{P h} u ^ k ^p nymph ěoy 5 is ^{0%. The} film showed no formation of holes and bubbles and had a closed surface.

After the 5 tonne throughput, there were no deposits in the dosing organs and the shock.

If nulkleační agent were deposited on the granulate as usual and in this form fed into the extruder, the foamed sheet mmiy following properties and appearance: pore diameter varied ^{in the} dimension ^ i ^ i from ^0.1 to 1, ⁰ mm, the average number p · ^r ru ^l číoí ¹ OA 5 ^{mm2. p} ovrc ^h has not been completely closed. After passing 200 kg of mixer, over 100 kg of nucleating agent were deposited in the conveying routes. After passing through 5 tons, deposits of the worm appeared.

EXAMPLE 3 mm silo pěoová plate that consisted of 60 parts of a copolymer etyléovioylacetátu containing 5% CmoStιostnícC vioylacetátu and 40 parts of polyethylene and had a specific weight ^of ost ^0, 25g / ^c rn ^m, stalks crushed in ^d ^ t ^ichi OA insert ^ y. The ^foam flakes had a specific gravity of ^0.1 g / cm & lt ^; 3 > kg of these foam flakes were mixed in a rotary mixer with 225 g of citric acid, 225 g of carbonate, sodium, 1050 g of cadmium citric yellow and 350 g of red iron. . The stirring time was 30 minutes.

The mixture was fed through a weighing scale into a twin-screw extruder. Despite the second dosing weight, the feed mixture consisted of granular polyethylene (40% by weight) and ethylene acetate acetate copolymer. with 5% w / w ethyl acetate (60% w / w) into the extruder.

5 kg of foamed flakes were dosed per 50 kg of granulated granules and the ingredients were adsorbed. The treatment of the samples was carried out analogously to Example 1.

The obtained foam sheet showed no hole formation and bubbio, had uniform cells, 2 with a diameter of 0.005 to 0.5 mm and an average pore number of 50 o and mm. The proportion of open cells on the surface of the puff flakes was 90%. The coloring was uniform. No differences in color tone were detectable visually between the foam sheets made of six different compositions. No deposits were formed in the conveying, pumping or extruder sections.

Example A 4 mm thick foam plate consisting of 60 parts of an ethylene vinyl acetate copolymer containing 5% by weight of vinyl acetate and 40 parts of polyethylene and having a specific gravity of 0.25 g / cm < 3 > was crushed in a flake crusher. The foam flakes had a bulk density of 0.1 g / cm < 3 > kg of these foam flakes were mixed in a rotary mixer with 120 g of citric acid, 360 g of sodium bicarbonate, 1,050 g of cadmium citric yellow and 450 g of ferric red. The mixing time was 30 minutes. The mixture was fed to a twin-screw extruder via a dosing scale. A mixture of granular polyethylene (40% by weight) and an ethylene-vinyl acetate copolymer with 5% by weight vinyl acetate (60% by weight) was dosed through the second dosing weight to the extruder.

5 kg of foam flakes were added per 50 kg of the granulated mixture on which the additives were adsorbed. Processing of the mixture in the extruder was carried out analogously to Example 1.

The obtained foam films did not show holes and bubbles, they had uniform foam cells with a diameter below 0.1 mm and an average number of pores above 50 per mm ^{1 2} . The proportion of open cells on the surface of the foam flakes was 95. The coloring was uniform. No differences were visually detectable between the foam sheets made of six different compositions. *

No deposits were formed in the conveying and pumping equipment as well as on the extruder screws.

Example 5 kg of polyethylene foam flakes, 5 kg of polyethylene granulate and 1500 g of white pigment were mixed according to Example 1. Addition of polyethylene granulate to the color mixture improved the dosability of this mixture. The color mixture was fed through a dosing scale into the extruder. A polyethylene granulate was fed into the extruder through a second dosing weight, and 25 g of a color mixture was fed to 180 g of polyethylene. The extruder used had a screw with a diameter of 60 mm and a length of 25 D. It was provided with a feed area, a degassing area and two compression areas. The throughput was 40 kg / h. The obtained granulate showed a perfect dye distribution. In the thin film test, no pigment agglomerates with a diameter above 50 mm were found. The granulate grains showed no gas inclusions.

The proportion of open cells in the surface of the foam flakes in this case was 80%.

Claims (2)

SUBJECT OF THE INVENTION Process for incorporating additives into polymers, wherein the mixture consisting of one or more thermoplastics with the necessary additives is heated to a temperature sufficient to melt it, optionally introducing a blowing agent into the melt, which is homogenized therewith, the melt is cooled to a temperature at which which is optionally extrudable as a foam, characterized in that the additives are adsorbed onto a polymeric flake matrix of polyethylene or a mixture composed of a copolymer of polyethylene and ethylene, or a mixture of polymeric flake matrix and polymer granulate having a specific gravity up to 0.6 g / cm < 3 >, an open cell fraction of 50-95% and the same or different composition of polymers than the parent polymer. 2. A method according to claim 1, wherein: se. by the use of citric acid and carbonate as additives, wherein 1.5 to 15 moles, preferably 2 to 6 moles of bicarbonate or 0.8 to 7.5 moles, preferably 1 to 3 are adsorbed per mass equivalent of organic acid moles of carbonate.