WO2006007677A1

WO2006007677A1 - Process for obtaining a porous matrix using a chemical additive

Info

Publication number: WO2006007677A1
Application number: PCT/BR2005/000127
Authority: WO
Inventors: Aniceto Alves Braga
Original assignee: Deltacap 430 Participacões Ltda
Priority date: 2004-07-16
Filing date: 2005-07-13
Publication date: 2006-01-26
Also published as: AR049991A1

Abstract

The present invention is related to a production process of porous matrixes, chemical additives for the obtainment thereof, coatings of polymeric matrixes, obtained matrixes and articles that comprise said porous polymeric matrixes; substances capable of forming gases in the polymeric composition are added during the matrix polymerization process, generating pores in the matrix.

Description

Process for Obtaining a Porous Matrix, Chemical Additive

Field of Invention

The present invention is related to production processes of porous polymeric matrixes and products resulting from said processes, being also related to articles comprising said polymeric matrixes. The present invention is also related to chemical additives useful in the preparation of said porous polymeric matrixes and porous coatings for polymeric matrixes.

Background of Invention

In the last decades, the market of synthetic materials had suffered many changes. There is a high demand by development of new material that can substitute or improve natural materials. In general, new materials that present advantage characteristics as high resistance and lightness beyond low obtaining costs are desirable. Another desirable characteristic of the substitutes is a high similarity with the reference natural materials. However, up to the moment, materials that try to substitute the materials originated from the nature had not reproduced efficiently the desirable characteristics thereof. In the case of materials whose application is in substitution of leather, one of the characteristics of hard obtainment is the porosity in the synthetic materials. In many products, material porosity is extremely important, since this characteristic is responsible for product's transpiration, absorption and "touch ability". Depending on the kind of product and the intended application thereof, the size of the pores can vary, many times being desirable the micro pores, since they are visually imperceptible and can give to the material selective permeability characteristics.

There are many applications to the polymeric matrixes. One of them is the utilization of synthetic laminates as substitutes of leather of animal. This application has been studied in view of producing an ecologically correct raw material, cheaper and with visual and touchable aspects similar to the natural leather. Conventional synthetic leathers, made of plastic material laminates, as those formed by an abrasive foam layer adhered to the substrate, usually comprising a lamination of polymeric element sheet in a substrate. These methods significantly decreases the product costs, when compared to products of natural leather, but present disadvantages related to durability and quality, not being therefore, competitive or with good appeals to the costumers.

Techniques that are currently used to produce said synthetic laminates are known as calendering, thermoforming and spread coating and others. However, for some specific applications, like the utilization of this laminates as substitutes of the natural leather, the currently available production processes do not give to the products any high desirable characteristics, like permeability, absorption, surface smoothness, appearance and "touch ability". On the other hand, is known by skilled in the art that such characteristics are related to the porous structure, and up to now, products with porous structure could not be obtained through production processes of synthetic laminates above mentioned.

There are porous synthetic laminates available in the market, whose pores has been produced by complex stages or posterior stages to the lamination of polymeric elements, increasing the time and the cost of the production process thereof.

US patent 3,841,897 of Toray Industries, Inc., discloses the interest in obtaining a porous structure in synthetic leathers. Said patent discloses synthetic leather comprising a substrate and 3 coating layers adhered on it, and 2 of these 3 layers have insoluble and inorganic particles to give porosity to the layer. However, the process is complex and the obtained porosity is limited, since the product has no especial properties of permeability and absorption. US 6,152,001 patent of Heinz Faustmann, discloses a process for the perforation of different sheet material through the transport of said sheet by a conveyor containing spike rollers. However, the use of said spike rollers has operational disadvantages, which has no capability of forming laminated polymeric materials with micro pores.

US 5,356,497 patent of Chi S. Lee, discloses a method for forming a porous laminated material, which consists of discharging static electricity in the laminated material after its formation, to form several many pores in the product. However, said process needs additional steps of forming the holes, further implicating in additional costs of electric energy.

Process for obtaining matrixes constituted by polyurethane and containing pores are known. However, currently available processes present several disadvantages, such as elevated costs of industrial installation like coagulation towers and operation thereof, and limitations related to the thickness of matrix that can be obtained by this processes in the porous form.

Synthetic laminates usually need a complement, even for the visual appeal as for the protection. The complement normally used is a covering made by a material similar to that that was laminated. However, the coverings (coatings or lackers), developed up to now, are not porous or can not keep the matrix porosity, in which such coverings are applied. On this context, the use of formerly available coatings on the porous matrixes caused undesirable problems, such as obstruction or blockade of the matrix pores, causing the loose of transpiration and absorption characteristics by the product.

The currently available alternative to application of the coatings on porous matrixes is the utilization of the system called by 1000 points, which consists of applying the coating only on part of the surface, thus requiring an equipment specific for that and additional production costs. Therefore, up to the present invention presentation, there were not known even processes for giving porosity to synthetic materials in a single step with high efficiency, or processes for giving porosity to coatings of porous synthetic material. The present invention overcomes this and others difficulties presenting a process for the production of porous synthetic materials in a single production step, needing no special equipments and not causing operational complexity. Products obtained by the process of the present invention present properties that are comparable from natural leather. In other words, present invention bypass several problems of the state of the art, providing a simple industrial process and a material, which has elevated and controlled porosity, providing advantages either to process or product.

Additionally, simple processes for application of complement and/or coating layers capable of maintaining the porosity in porous matrixes were not yet described by the state of the art. Therefore, the present invention solves this problem presenting a porous coating, keeping the capability of transpiration and absorption of porous matrixes.

SUMMARY OF THE INVENTION

It is an object of the present invention providing a process with low costs for the production of porous polymeric matrixes. In an aspect, being therefore, one of the objects of the invention, said process enable formation of porous polymeric matrixes in a single step, requiring no posterior introduction steps of pores to the formed matrix and demanding no sophisticated or expensive reactants, beyond the gas formers.

Another object of the present invention is providing a chemical additive, which has the capability of arousing the formation of gas in the polymeric matrix, forming pores therein.

In other aspect, being therefore, other object of the present invention, the present production process of porous polymeric matrixes permits the easy control of different operational conditions through the choice of suitable mixture of polymeric ingredients and gas former agents, to the formed pores pattern can be adjusted in accordance with the gas formation and/or diffusion condition through the porous polymeric matrix.

In a further other aspect, being therefore, other object of the present invention, the present production process of polymeric matrixes dispenses the need of hard investments in industrial installations, because it is easily applicable to already existents conventional industrial installations to the production of non-porous polymeric matrixes.

Said porous polymeric matrix is useful in several applications, notably as substitute of natural leather. Therefore, it is another object of the present invention to provide a porous polymeric matrix that presents characteristics very closed to that from natural leather, including, among others, aspect, "touch ability", texture, resistance and permeability or transpiration. The skilled in the art will verify that tests described on the present invention are those executed in synthetic laminates and/or in leather from animal origin, including permeability, color consistence, abrasion, rupture, tension, elongation and porosity, among others. In other aspect, polymeric matrix of the present invention is useful in the confection of several articles of practical use. Therefore, the articles that comprise said porous polymeric matrix are also objects of the present invention. In other further aspect, being therefore other object of the present invention, polymeric matrixes of the present invention present pore that enable special conditions to the control of gas and liquid diffusion through the matrixes.

In the production of conventional synthetic laminates, protection and/or decorative coverings are desirable. In a special aspect, some porous synthetic laminates can require a special coating to do not loosing highly desirable transpiration and absorption characteristics. Thus, it is an additional object of the present invention providing a porous coating composition to porous synthetic laminates.

This and other objects of the present invention will be more apparent to the skilled in the art from the detailed description of the invention and from the claims.

BRIEF DECRIPTION OF THE FIGURES

Figure 1 illustrates a schematic example of a spread coating. Figure 2 is a schematic representation of the porous structure transversal section, where 11 is the porous part and 12 is a fabric that supports it.

DETAILED DESCRIPTION OF THE INVENTION

One of the main objectives of the present invention is present a new process for the production of porous matrixes. For the effect of the present invention, it is understood by "matrix" a matrix formed entire or partially by polymeric elements, like PVC (polyvinyl chloride), PU (polyurethane), combinations thereof, and other materials that can be laminated (receive the denomination of synthetic laminates) by spread coating, calendering, thermoforming or combinations thereof.

The inventors have developed a process for pores formation in matrixes that can be produced in conventional processes of spread coating (Figure 1). The process consists of incorporating, to the material to be spread coated, of chemical additives that have the capability of arousing the gas formation in a controllable manner, inserting pores to the polymeric matrix during production process thereof. To the present invention ends, the terms "chemical additive" refers to substances that are capable of arousing the gases formation in the production conditions of polymeric matrixes. Having the knowledge of the present invention, the skilled in the art will verify that several substances are potentially useful as chemical additives for the present invention, being preferred those that are compatible to polymeric material to be spread coated and do not arouse the formation of undesirable sub products. Therefore, in the present invention's process, the formation of gases occurs before the end of production process of a polymeric matrix. Thus, gases formed inside the polymeric matrix and, by diffusion, elevate through the matrix, inserting micro pores to the matrix.

Physical characteristics of the polymeric matrix obtained by the process of the present invention (like, e.g., absorption, permeability and flexion resistance) can be easily controlled according to the process conditions. In the present invention it is understood by "process conditions" the concentration control parameters of resin/polymer, charge fraction (e.g. calcium carbonate) in the composition, use proportion of chemical additive, temperature control and/or residence time in the furnace or oven. Depending of the process conduction condition, it is possible controlling the diameter and/or amount of formed micro pores, in view to obtain a final product with the desirable characteristics of the intended application. The composition can further contain other components that increase the characteristics spectrum of the final product, like, for example, substances with fungicide and/or bactericide action and modulator agents of odor, among others.

One of the utilization forms of said polymeric matrix is in the production of articles that can be manufactured with natural leather or synthetic leather. On this aspect, some invention applications include the use of said porous polymeric matrix in shoes, domestic and car stuffing, wear articles and several other articles that use similar materials. To give an incremented visual aspect to the product, matrix can be endowed with coating. This is a process known by the skilled in the art in non-porous synthetic laminates, being that available to the coating application on matrixes or porous laminates (of polyurethane) dependent of sophisticated and expensive equipments, according previously described in the background of the invention. However, conventional processes of coating application on porous laminates arouse the loosing of transpiration and absorption essential characteristics. In view of overcome these difficulties, the inventors have developed a coating that does not dismiss the laminates from these highly desirable characteristics. The coatings (lackers) described by present invention are equally porous. The pores formation process in said coating is similar to the pores formation process of the porous polymeric matrix previously described. Chemical additives that arouse gases formation are utilized, providing the coating with pores. The coating application process of the present invention is simple, cheap and easily adapted to already existents industrial installations. Additionally, the coating application process of the present invention enable a better thickness control flexibility of the present invention, thus modifying no desirable porosity characteristics.

The following examples have the intention to illustrate, but do not limit the embodiment forms of the present invention.

Example 1

The process of the present invention was tested in the production of porous polymeric matrixes in conventional spread coating process. The spread coating process consists of analyzing a polymeric material surface disposed on a conductor. To the present invention ends, it is understood by "conductor", a siliconated paper, a fabric or similar material. The conductor is placed in a spread coating agent, like that illustrated in Figure 1, serving the support of the application of the polymeric material. After the application of the polymeric material, in liquid state and yet at the conductor, the spread coating of said mass is done to obtain a homogeneous surface. The skilled in the art will verify that the polymeric material layer can have different thickness, according to intended application, and the homogenization of said layer can be done by cylinders or by equivalent devices. Following that, the conductor containing the polymeric material on its surface is conduced to one or more ovens where temperature is controlled to polymeric material is cured up to desired grade.

In the process of the present invention, a chemical additive is added to the polymeric material composition, the mixture being homogenized and applied in a conventional spread coating process, as above cited. The chemical additive of the present invention is any substance or substances mixture which has the capability of arousing the formation of gas in the polymeric mass, since it is compatible to the polymeric material and/or does not form sub products that degrade or harm the quality thereof. Preferred additives of the present invention are those that arouse gas formation only in specific and controlled conditions, as for example temperature. In the present illustrative example, the conductor, on where the polymeric mass containing said chemical additive is spread coated, pass by an oven where heat is provided to the system. Since in the ambient exemplified herein, the chemical additive used is a combination of a acrylamide (celube) and ammonium, the temperature conditions offered by the oven are ideal to accelerate a chemical reaction in the polymeric mass, generating gas and consequently forming micro bubbles in polymeric matrix. Although gases formation mechanisms are not essential to the application of the present invention and are not completely explained, it is believed that diffusion of the formed gas occurs up to outlet of the polymeric matrix.

The following table presents an example of combination of inputs and respective utilized concentrations.

Table 1: Polymeric material and gas-forming composition

The obtained product from the above described process was submitted to several tests. To check the selective permeability, there were executed tests in pressure chamber. Said test consists of putting the product between two recipients, the bottom recipient has a little pump. The test consists of filling the recipient of the superior part with water and insufflating air in the inferior recipient, creating a pressure intermediate situation. In case the polymeric matrix situated between two recipients is permeable, it will be observed the elevation of the bubbles in the superior recipient. In the tests executed with the resulting product of said example, the elevation of bubbles was noted. Analyzing the faces of the formed laminate, we conclude that the permeability is different to the faces. The pressure test results suggest that the obtained product has selective permeability, in other words, it is permeable to little molecules (gases) and it is not permeable to aggregated molecules (liquids).

Example 2

The described coatings of the present invention, also known by skilled in the art by lackers, are also endowed with pores and, therefore, have the capability of keeping the porosity characteristics of the porous polymeric matrixes. The pores formation process in said coating is similar to the pores formation process of the porous matrix previously described. Chemical substances are added to components of the coating that, forming gases, release to external means inserting pores in the coating.

The present invention process was tested in the production of polymeric matrixes coatings in conventional spread coating process. A conductor, preferably rugged, is placed in a spread coating agent as that illustrated in Figure 1 , serving of support for the application of the polymeric material coating. After application of the polymeric material coating, still in liquid estate at the conductor, it is done the spread coating of said coating to obtain a homogeneous surface. The skilled in the art will verify that a coating layer can have different thickness, according different intended applications, and that said coating homogenization can be made by cylinders or by equivalent devices. Thus, the polymeric mass described in Example 1 can be added on the conductor containing the coating layer, being conduced to one or more ovens, where temperature is controlled until the coating and/or polymeric material is (are) cured up to desired grade.

In the present invention's process, a chemical additive is added to the coating composition, being the mixture homogenized and applied in a conventional spread coating process, as above cited. Said chemical additive is any substance or substances mixture that has (have) the capability of forming gas in the coating, since it (they) is (are) compatible to coating and/or polymeric material and/or forming no sub products that degrade or damage the quality thereof. Preferable additives of the present invention are those that provide only the gas formation in specific and controlled conditions, like, for example, temperature. In the present illustrative example, the conductor, on which the coating is spread coated containing a chemical additive and the polymeric mass containing a chemical additive, passes by an oven where heat is provided to the system. Since, in the ambient herein exemplified the used chemical additive is a combination of a acrylamide (celube) and ammonium, the temperature conditions offered by the oven are ideal to accelerate chemical reactions in the coating and in the polymeric mass, generating gases and bringing, as consequence, the micro bubble formation in the coating and in the polymeric mass.

Knowing the present invention, the skilled in the art will verify that several substances are potentially useful as chemical additives to concretize this invention aspect, being preferred those that do not provide undesirable sub products formation when mixed to other coating components. The following table presents the used inputs to the formation of the coating endowed with pores of the present example and the respective concentrations.

Tabela 2: Coating composition of the porous matrix and of the gas-forming additive.

Example 3

Present invention process was tested also in the polyurethane-containing porous polymeric matrixes production in convention spread coating process. The spread coating process of the present example is similar to those described in previous examples, differing that said chemical additive is added to a polyurethane-containing polymeric material composition. The skilled in the art will verify that pores-endowed polyurethane-containing matrixes obtainment in a conventional spread coating process is highly advantageous and desirable, notably if takes in consideration the elevated costs of installation which involve the production of alternative processes, e.g. the coagulation towers. In the present example, it can be obtained a porous polymeric matrix comprising one or more porous polyurethane layers and one or more PVC porous layers, when the addition of respective polymeric masses containing the respective chemical additives in successive steps is executed. Optionally, said porous polymeric matrix can additionally comprise one or more layers of porous coating, according to illustrated in example 2. The skilled in the art will appreciate that the obtained product with this example process can be applied with advantages in the shoes production. The skilled in the art will also appreciate that:

(i) PVC porous polymeric matrix whose thickness can be reasonable high, not loosing porosity or advantageous characteristics thereof; combined with

(ii) polyurethane porous polymeric matrix, whose properties (like, for example, better appearance) give desirable complement to external parts of a shoe, constitute a product with highly advantageous characteristics to shoe industry, and before the present invention, the obtainment was not possible. A product with these combined characteristics can, for example, be used shoe leathers and/or in other industrial sectors that use this kind of material.

Example 4 - Assays results

A product sample obtained by the process of the example 1 , having the thickness of 0.9 mm, was submitted to following standard tests used by national and international certifiers.

Determination of the permeability to Water Steam (EN 344:1997 - item 5.13.1) - 5.0 mg/cm²h.

Complement resistance to friction with Fabric (NBR 14367:1999) - Grade 5, absence of contrast (no stain or tarnish), as shown in table 3.

Table 3: Tests results in laboratory.

"Color" solidness to the perspiration (ISO 11641 :1993) - Grade 5, absence of contrast (no stain or tarnish), as shown in table 4. Table 4: Results of the laboratories' tests

Resistance to the rip continuation (NBR 14553:200) - average of 27 N in both directions, as shown in table 5.

Table 5: Tests results in laboratory.

Table 6: Tests results in laboratory - Resistance of the material to needlework, dynamic assay.

Table 7: Tests results in laboratory - Resistance to traction and elongation in the rupture.

According to the PFI (Assays and Researches to the Shoe Production Institute - Germany), this results give to the product suitable characteristics to synthetic laminates for use in shoes liner, both security and daily use.

Example 5 - Assays results

A product sample obtained by the process of the example 1 , having the thickness of 1.5 mm, was submitted to the following standard tests used by national and international certifiers.

Permeability determination to Water Steam (EN 344:1997 - item 5.13.2) - 0.2 mg/cm²h. Behavior of continuous flexion - Dry (DIN 53351 :2003) - 2, as shown on table

8.

Table 8: Tests results in laboratory.

Example 6 - Assays results

A product sample obtained by the process of the example 1 , having the thickness of 1.0 mm, was submitted to the following standard tests used by national and international certifiers.

Determination of the permeability to Water Steam (EN 344:1997 - item 5.13.1) - 2.4 mg/cm²h.

Determination of the absorption to Water Steam (EN 344:1997 - item 5.13.1) - 2.4 mg/cm²h.

The skilled in the art will verify that other forms of concretizing the present invention are possible from this description and that little changes in the process conduction form herein described should be comprised as part of the invention idea and the attached claimed scope.

Claims

ClaimsProcess for Obtaining a Porous Matrix, Chemical Additive, Coating for PorousMatrix, Porous Matrix and Articles

1. Process for obtaining porous polymeric matrixes, characterized in that comprises the steps of:

- adding to a composition capable of polymerizing one or more chemical additives capable of arousing gas formation in said composition; and - providing conditions to said chemical additive arouses gas formation during the polymerization process of a polymeric matrix, forming pores in said matrix.

2. Process according to claim 1 , wherein said chemical additive is a combination of an acrylamide and ammonium.

3. Process according to claim 1, wherein said composition capable of polymerizing is homogenized with said chemical additive and spread coated in a conventional spread coating process.

4. Process according to claim 1, wherein said composition capable of polymerizing comprises polyvinyl chloride, polyurethane, combinations thereof or other polymers.

5. Process according to claim 1, wherein said composition capable of polymerizing comprises conventional coatings and/or lackers.

6. Process according to claim 1, wherein said composition capable of polymerizing further comprises at least one adjuvant chosen from the group that comprises lubrification agents, stabilizing agents, plastifying agents or combinations thereof.

7. Process according to claim 1 , wherein said composition capable of polymerizing further comprises substances chosen from the group that comprises fungicides, bactericides agents, odor modulator agents or combinations thereof.

8. Chemical additive for the obtainment of porous polymeric matrix characterized in that comprises substances endowed with property of arousing gas formation during the polymerization process of a polymeric matrix, forming pores in said matrix.

9. Chemical additive according to claim 8, wherein comprises a combination of an acrylamide and ammonium.

10. Porous matrix of polymeric material characterized in that comprises pores formed by gases generated during polymerization process of said matrix.

11. Porous matrix according to claim 10, wherein said polymeric material comprises polyvinyl chloride, polyurethane, combinations thereof or other polymers.

12. Coating for porous matrixes characterized in that comprises pores formed by gases generated during the polymerization process of said coating.

13. Article of domestic or industrial use characterized in that comprises at least one porous polymeric matrix comprising pores formed by gases generated during the polymerization process of said matrix.

14. Article according to claim 13, wherein is applied to shoes liner.

15. Article according to claim 13, wherein is applied to shoes funds.