MXPA98002577A - Foamable articles reticulab - Google Patents

Abstract

The present invention relates to the method of manufacturing crosslinkable and foamed extruded products from formulations of Polyvinyl Chloride (PVC) or other similar polymers. The polymer is fed in a screw extrusion machine together with the other ingredients of the formulation, which comprise a crosslinking system, thermal stabilizers, lubricants and catalysts. The ingredients are previously mixed in an intensive mixer, to be subsequently fed and melted in the extruder, where they are heated sufficiently to carry out the extrusion of the polymer. It is important to establish the necessary concentrations of stabilizers and crosslinking system that are required to prevent premature crosslinking (crosslinking) of the polymer, so that extrusion of the polymer is impossible. The mixture is extruded directly through a forming die, which imparts the desired shape to the article, the cross-linking and foaming is carried out, subsequently, by the action of heat. In the case of formulations with PVC emulsion, the preparation of the plastisol is carried out, its formation by dip coating or casting and subsequently curing and foaming by the action of heat. In this case, it is also important to establish the optimal concentrations of the cross-linking system in order to obtain a foam with the appropriate characteristics.

Description

RETICULABLE FOAM ARTICLES * W DESCRIPTION: The present invention relates to the manufacture of crosslinkable foamed products, especially, but not exclusively, of automotive moldings and thermal insulation; which are made from chlorinated hydrocarbon chain polymers and are crosslinked by the joint action of compounds derived from triazines, multifunctional compounds and organic peroxides and are -t_r_ foamed by chemical agents. Also applicable for mixtures of ? 10 PVC with other polymers. These products are basically processed in a one-stage process: in which the PVC polymer or its analogs (ethylene vinyl acetate copolymers, etc.), or mixtures of PVC with other polymers, react in a curing oven with the compound derived from triazine of general formula wherein Z represents a phenyl radical, optionally substituted once or twice by alkyl groups containing from 1 to 5 carbon atoms, or groups in which R, represents a linear or branched alkyl radical and R2 and R3, which can be the same or different; each represents a hydrogen atom, a linear or branched alkyl radical containing from 1 to 18 carbon atoms, a benzyl radical or a cycloalkyl radical.

Through this manufacturing process, it is also possible to incorporate an unsaturated polyfunctional monomer and an organic peroxide; the polyfunctional monomer may be an acrylic, methacrylic monomer or similar compounds, such as, trimethylolpropanetrimethacrylate. The organic peroxide of the general formula R-O-O-R ', wherein R and R' may be an alkyl or aryl radical.

The method described in the present invention also provides a crosslinking process for products previously described, reinforced or filled with inorganic fillers and containing pigments (both organic and inorganic).

The manufacture of crosslinkable foamed products by the technique of incorporation of reactive chemical agents and their subsequent cross-linking and foaming is carried out in a two-stage process: first the polymer is formulated with the additives of the formulation, which can be plasticizers, stabilizers thermics, lubricants, foaming agents and reactive groups, in this case the triazine derivatives, the polyfunctional monomers and the peroxide. The formulation can * be processed by traditional methods used for the processing of plastics (extrusion, injection, rotomoideo, etc.), in this stage is given the desired shape (coating of cable, pipe, sheet, filament etc.) and, subsequently, the finished article is reticulated and foam, preferably subjecting it to the action of heat.

According to this invention, the method for manufacturing extruded products crosslinkable foams comprises: preparation of a formula containing the polymer, the triazine derivatives, the polyfunctional monomer and the organic peroxide. Premature crosslinking is eliminated by properly selecting the type and concentration of the crosslinking system, as well as, the appropriate temperatures. During processing, the molten mixture of the material passes through a die, which gives it the desired shape; the final cross-linking and foaming of the functionalized polymer is carried out by the action of heat.

Normally no rigorous removal of moisture from the Mixing before extrusion but, as in any conventional extrusion process, large amounts of water must not be present. If required, the crosslinking reaction can be carried out at temperatures below the deformation temperature of the grafted polymer, and in this way avoid distortion. * It is possible to add other components to the formulation, such as fillers, pigments, dyes, antioxidants, etc.

The preparation of the polymer mixture, with the other ingredients of the formulation, is carried out in an intensive mixer, which normally works at high revolutions. The polymer is preheated to a temperature of 80-110 ° C, # ío preferably 80 ° C for a time that can range from 10 to 25 minutes. After preheating, dissolved liquid components are added in a plasticizer (phthalic anhydride derivatives, or trimellitic acid derivatives can be used), leaving the mixture to a temperature of 100-120 ° C. Once this temperature is reached, the mixture is discharged and allowed to cool, careful not to absorb moisture. If components such as fillers or colorants are used, they can be added before the stage of adding the plasticizers.

In the case of formulations for plastisols, the mixture is prepared in a mixer equipped with ribbon-type blades, first add the liquid additives and the plasticizer and mix for a period of time of 2 to 10 minutes, then add, little by little, the solid additives and mix for a period of 5 minutes. at 15 minutes, the total mixing time can be in the range of 20 to 45 minutes. The formulations thus prepared can be used in a dip coating process, which is described: an object of the desired shape is immersed in a container containing the plastisol, the immersion can be carried out cold or hot, it is usually they obtain better results with hot dip, since the layer immediately after the object is partially cured and this helps to control the thickness of the layer. Molding by emptying. In this operation the mold is heated and filled with plastisol, which solidifies in contact with the hot wall. After a certain gelation time, the excess fluid is removed and reintroduced to an oven for curing.

For the case of suspension or mass PVC formulations it is necessary to pass the formulation prepared by an extrusion process, which is described: The extruder has a barrel, which is equipped with a screw; the screw can be composed of different sections, to increase the mixing and promote the fusion and the functionalization reaction, the screw can also be designed with intermediate sections without helical turns (as for example the two-stage screws that are used in the extruders with venting). The extruder should have a mixing zone, a homogenization zone and a dosing or pumping zone.

From the dosing zone of the extruder, the chemically modified and homogenized polymer passes to the extrusion die. A different die will be used depending on the product to be obtained: profiles, sheets, filament, etc., for the case of wire coating a cross type die is used. The finished product can be crosslinked and foamed by the action of the temperature.

The method of this invention avoids the need to use high temperatures to carry out the crosslinking. Furthermore, it has been found that it is possible to vary the crosslink density and the degree of crosslinking depending on the ratios of the different chemical agents that are used in the formulation, whether they are peroxides, triazine derivatives, polyfunctional compounds or thermal stabilizers. In the following examples, some of the physical properties of the foamed and crosslinked materials are specified by the method object of this invention. The measurements are based on standardized tests.

«EXAMPLE 1 Polyvinyl chloride (PVC) suspension resin with a value of K = 70, plasticizer: di-2 ethyl hexyl phthalate, lubricants: stearic acid and calcium stearate. The parts are expressed in parts per hundred of resin (per) 20 Plasticizer 30-100 per Lubricant 1-5 Thermal stabilizer 3-9 Polyfunctional Monomer 1-10 Foaming Agent 1-8 Activator 0.5 -10 Sist. crosslinker / initiator 3 - 7 / 0.5 - 5 The extruder has a length: diameter ratio of 24: 1 and has a feed area of approximately 8 diameters, followed by a homogenization zone of 10 diameters, followed by a dosing zone of 6 p diameters. The temperature of the barrel was kept below 140 ° C, including the temperature of the forming die.

The properties obtained after crosslinking the material for 10 minutes at 180 ° C, in a hot air oven, were the following: Gel content 40% Tensile strength 2.0 Mpa Elongation at break 250% Softening point 105 ° C 20 EXAMPLE 2 It is similar to example no 1, except that the crossover was carried out at 200 ° C Gel content 50% Tensile strength 5.4 Mpa Elongation at break 250% Softening point 115 ° C # 10 EXAMPLES 3 - 5 Examples 3-5 are similar to 1 except that different Activator contents (1, 3.5%). The physical properties were very similar to the obtained in example 1.

Catalyst% • 1 3 5 Gel content (%) 40 43 45 Tensile strength MPa 20 21 21.5 20 Elongation at break (%) 2 > 5500 230 230 Softening point (° C) 1 10055 105 108 EXAMPLE 6 Polyvinyl chloride (PVC) type emulsion with a value of K = 66, plasticizer di-2 ethyl hexyl phthalate (DOP), calcium stearate lubricant 5 Plasticizer 30-100 per Lubricant 1-5 Thermal stabilizer (octyl tin) 3- 9 Functional monomer 10 fik Foaming agent (azodicarbonamide) 1-8 Activator (Ba / Zn stearate) 0.5 -10 Organic peroxide 1 - 5 The mixture is prepared following the method described for the preparation of plastisols. Then, the plastisol is deposited on a stainless steel sheet and is introduced into an oven with hot air circulation to carry out the crosslinking of the material.

The properties obtained after crosslinking the material by exposure to heat were as follows: 20 Gel content 30% Tensile strength 1.0 Mpa Elongation at break 250% Softening point 85 ° C EXAMPLES 7 -9 Examples 7 to 9 are similar to example 6, except that they were used > different contents of trifunctional monomer (10.15 and 20%) and peroxide (1 and 3%). The properties obtained after crosslinking the material obtained at 195 ° C are 5 as follows: Monomer / Peroxide Ratio 10/1 15/1 20/1 10/3 15/3 20/3 Gel content (%) 8.5 15 20 12 25 35 Tensile Strength (MPa) 0.9 1.6 2.2 1.8 2.4 2.8 * Elongation at break (%) 175 200 200 100 100 100 Having described the present invention, it is understood that there may be modifications and variations without departing from the spirit of the invention; such variations and modifications are considered within the scope of the present invention, which is considered a novelty and therefore is claimed as A- ownership the content in the following claims:

Claims (9)

1. - A method of manufacturing reticular foamed products, which comprises: 5 Intensive mixing of the polymer (PVC or its analogues or mixtures of PVC with other polymers) with plasticizers and other ingredients of the formulation, these ingredients comprise lubricants, and essentially a WM polyfunctional compound containing double bonds, may contain

10 also colorants or mineral fillers. The basic ingredients are the derivative of triazine and the polyfunctional compound, which may contain double bonds that, in the presence of peroxides, are capable of reacting with the polymer at extrusion temperatures; as well as, the incorporation of the foaming agent. fifteen

«The mixing of the polymer with plasticizers and other ingredients of the formulation, to obtain a plastisol. The important ingredients are the triazine derivative and the polyfunctional compound to carry out the crosslinking reaction in the presence of the initiator. The incorporation of the chemical foaming agent is of vital importance for obtaining the foamed material.

n Feeding to an extruder of the formula previously prepared, to carry out the fusion and reaction to functionalization. The fundamental parameters to be controlled in the extruder are residence times and temperatures to avoid premature cross-linking of the polymer.

Extrusion through a die forming, either to cover electrical cable, produce pipe, filament or flat sheets.

Obtaining plastisols for coating by immersion or cast molding.

Cross-linking and foaming, of the article extruded and / or formed by the action of heat.

2. - A manufacturing method as indicated in claim 1, in which an extruder is used which successively contains a feeding zone, a homogenization zone, a dosing zone and a forming die.

3. - A manufacturing method as indicated in claim 1, in which the extruded product, sheet, pipe, filament, is subjected to the action of heat to carry out the crosslinking and foaming reaction.

4. - A manufacturing method as indicated in claim 1, in which a formula is used which contains among its ingredients filler, filler,

»Colorant and / or flame retardant and that can be processed by the methods described in this invention.

5

5. - A manufacturing method as indicated in claim 1, in which the catalyst of the reaction can be included in the formula.

6. - A manufacturing method as indicated in claim 1, in which

* Vinyl copolymers or mixtures of these with PVC can be used.

7. - A manufacturing method as indicated in claim 1, in which PVC or PVC mixtures can be used with other polymers.

15 8.- Obtaining PVC products and analogues with higher ßk tensile properties than similar articles without reticulating or foaming.

9. - The obtaining of flexible cross-linked PVC and analogous foams with improved tensile properties. twenty