WO2003018078A1

WO2003018078A1 - Curable compositions containing polymeric hydrogels and process for manufacturing technical articles and staples products therefrom

Info

Publication number: WO2003018078A1
Application number: PCT/RO2001/000016
Authority: WO
Inventors: Mihai Curtescu; Thierry Vanden Weghe
Original assignee: Mihai Curtescu; Thierry Vanden Weghe
Priority date: 2001-08-31
Filing date: 2001-08-31
Publication date: 2003-03-06

Abstract

The present invention relates to curable elastomeric compositions based on synthetical or/and natural elastomers, that contains adequate amounts of polymeric hydrogels from the class of polyacrylamides and to technical articles and staple products manufacture processes therefrom.

Description

curable compositions containing polymeric ydrogels and process for manufacturing technical articles and staples products therefrom

Background of the invention

The present invention relates to novel curable elastomeric compositions used for manufacturing, throughout specific curing processes, technical articles and staple products therefrom.

Description of Related Art

It is known that, for manufacturing technical articles and staple products from caoutchouc, elastomeric compositions comprising: synthetical and/or natural elastomers, zinc oxide, stearic acid, antioxidants, mineral batches and/or carbon black and/or cured caoutchouc powder (according to RO patent no. 69583), and/or plasticizers, sulphur and/or vulcanization accelerator (according to RO patent no. 88831 , 101438) are used.

These compositions are cured after allegation and/or milling and/or pressing processing with specific curing equipments, at temperatures varying from 119.5°C to 200°C, then after trimming and relaxation, technical articles and staple products such as: tires, rubber mats ( piece fabrics), conveyer belts ( with or without textile support), foot wearing soles (according to RO patent no. 100186, 105209), fittings, rubber sheets (from which different products are manufactured, for example: barges, hoops, insulations for different aggressive media, insulations for pipes transporting fluids - water or/and solutions and dispersions, slurries, etc -, sheets for foot wear soles, barge handles, rubber stanchions, hoses and so on ) are obtained.

Considerations over the state of art

The drawbacks of the curable elastomeric compositions already known consist of the presence, inside these compositions, of some products used as vulcanization accelerators, which are reactive chemical compounds from the class of tiurams, benzothiazole, sulphonamides, compounds that together with sulphur are cross-linking the elastomeric compositions at high temperatures (higher than 119°C).

All these substances have as a main inconvenience their high toxicity, most of them being catalogued as toxic substances (for example: insecticides, carcinogenic agents), thus arising the problem of professional diseases for the persons who manipulate them or work with them. Also, using high amounts of vulcanization accelerators and/or sulphur, for the purpose of reducing the curing energy consumption, in the crude or cured elastomeric compositions, an undesired exudation phenomenon of these substances in the environment takes. place . For this reason, the cured products thus obtained cannot be currently used in the nutritional and sanitary media, due to the exudation phenomena appear.

Nevertheless, due to the existence of some materials with different polarities (molecular dipole moment) in the already known curable elastomeric compositions, the cured products maintain internal tensions inside them, this providing them with a short exploitation period, compared to the products made from plastic materials.

The aim of the invention is to ameliorate these properties by modifying the already known curable elastomeric compositions and by making new products.

Summary of the invention

According to the present invention, the problems are solved using adequate amounts of polymeric hydrogels (in liquid or/ and solid shape) from the class of polyacrylamides in the curable elastomeric compositions based on synthetical or natural polymers; the polymeric hydrogels have the role of reducing the interfacial tensions from inside the compositions,.

By heating, these polymeric hydrogels loose a part of the water they contain, but the polywater remained in the grating provides them with reactive properties superior to the vulcanization agents already known, thus generating, in the curing grating of the synthetical or/and natural elastomeric compositions, a non-toxic plastic grating which is inserting and interreticulating in the curing grating of the elastomers. This grating is developing with a much higher speed than that of the rubber curing grating and at lower temperatures ( the loose of water starts at the ambient temperature and becomes insignificant at temperatures varying in the interval 170°C - 210°C when a stable thermodynamical equilibrium is established between the polyacrylamide and the resulted polyacrylic acid - regardless the initial constitution of the polymeric hydrogel or the hydrolysis rate of the initial polymer or its molecular weight, or the synthesis method used).

This fact is illustrated by the following thermodynamical equilibrium reaction (x): -CH₂-CH-CH₂-CH- + H₂0 - NH₃ + -CH₂-CH-CH₂-CH-

I I I I

CONH, CONH₂ CONH, COOH In the temperature interval studied by Zilberman and co. (Vysohomal, Soed. A., 19, 2714,1977), the equilibrium is established at a 60-70% PAA conversion rate, the reaction being self-accelerated due to the thermally formed carboxyl groups which become catalysts for the conversion of other amide groups.

Thus, at temperatures below 170°C, a macro polymer is forming in the curable elastomeric compositions, possessing rubber vulcanization accelerator characteristics (through the amide functional groups) as well as vulcanization activator characteristics (through the zinc carboxylate functional groups).

The cured products thus obtained have an elastic and/or plastic behavior, do not have internal tensions and the exudation of the accelerators or/and sulphur is reduced.

Detailed description of the invention The present invention relates to curable elastomeric compositions used for manufacturing technical articles and staple products therefrom.

It is known that, for manufacturing technical articles and staple products from caoutchouc, elastomeric compositions comprising: elastomers, zinc oxide, stearic acid, antioxidants, mineral batches, carbon black, plasticizers, sulphur , vulcanization accelerator, cured caoutchouc powder are used.

The drawbacks of the already known elastomeric compositions consist in the existence, during the technological treatment process, of one low velocity curing operation a, if cured products with good physico-mechanical and organoleptic properties (without cracks, exudations, etc)are needed; this operation is the slowest from the entire technological process, the terminal products having internal tensions.

The elastomeric compositions according to the invention eliminate the drawbacks presented above in that, in order to reduce the accelerator and sulphur exudation and the internal tensions in the cured products made therefrom, they consist of: 100 parts per weight synthetical and/or natural elastomers, 0 ... 240 parts per weight mineral batches (such as calcium carbonate, silicon dioxide, aluminum silicates or combinations thereof); 0.1 ... 5 parts per weight zinc oxide; 0.1 ... 4 parts per weight stearic acid; 0 ... 10 parts per weight resins ( such as colophon, highly styrene resins or coumarone indene resins or combinations thereof); 0 ... 4 parts per weight antioxidants ( such as phenol styrenate, phenyl-β-naphthyl amine or combinations thereof); 0 ... 240 parts per weight carbon black (impingement, furnace, synthesis or combinations thereof); up to 50 parts per weight cured caoutchouc powder; 0 ... 100 parts per weight plasticizer (such as mineral oils, grease, paraffin, dioctyl-phthalate, dioctyl-adipate, dioctyl- sebacate or combinations thereof); 0 ... 4 parts per weight sulphur; 0.1 ... 5 parts per weight vulcanization accelerators ( such as mercaptobenzothiazole, tetramethyl-tiuram- disulphide, N-cyclohexyl-benzothiazyl-2-sulphenamide, diphenylguanidine, benzothiazyl disulphide or combinations thereof); 0.1 ... 240 parts per weight polymeric hydrogel from the class of polyacrylamides having the following characteristics:

- average molecular weight: 2 10⁴ ... 5 O⁷ (kg/kmol):

- hydrolysis rate: 0 ... 100 (%);

- active dry substance content: 10 ... 75 (%).

The compositions obtained according to the invention have the following advantages:

- They reduce the curing time by enhancing the intensity of the energy and mass transfer, at the interface between the components of the mixture;

- They provide the cured products with physico-chemical characteristics superior to those obtained with the existing elastomeric compositions;

- They reduce the exudation of sulphur and of the vulcanization accelerators in the final product, by enhancing their reticulation degree;

- They reduce the internal tension in the cured products;

- They slightly increase the work capacity without the need of new equipments and endowments during the technological process for manufacturing rubber technical articles and staple products.

We give hereinafter 8 examples for producing the fast curing elastomeric compositions and the process for obtaining the cured products, according to the invention.

Example 1

The compositions used for manufacturing technical articles by curing, that are indicated in the Table 1 , are dosed.

The composition T₀ is the blank assay, in relation to which the comparison is made.

The polymeric hydrogel from the class of polyacrylamides used has the following main characteristics: average molecular weight: 8 - 10⁶ (kg/kmol) hydrolysis rate: 10 (%); active substance content: 42.0 (%).

Table 1 Elastomeric compositions containing activated silicon dioxide, obtained according to the invention

The compositions were feed on a roller in the order indicated in Table 1 and were processed for 12 ... 20 minutes, resulting sheets that were calendered at a thickness of 2 ... 3 (mm).

The following data concerning the curing times that are presented in Table 2 where obtained from the rheological characterization of samples of the produced sheets, at temperatures of 160°(C). Table 2 Technological processing times, for the produced mixtures, determined at temperatures of 160° (C)

Curing the sheets in the mould, at the electrical press at temperatures of 160 (°C) and acting over the mould with a pressure of 200 (daN/cm²), cured sheets were produced, that were characterized from the physico-mechanical point of view, the values presented in Table 3 being obtained.

Table 3 The main physico-mechanical characteristics of the produced cured sheets

It is noticed that the cured products that come from the mixture versions T_{1 ?} T₂ respectively have the main physico-chemical characteristics superior to those obtained for the mixture version T₀.

Example 2

The compositions used for manufacturing auto mats by curing, that are indicated in the Table 4, are dosed.

The composition M₀ is the blank assay, in relation to which the comparison is made.

The polymeric hydrogel from the class of polyacrylamides used has the following main characteristics:

- average molecular weight: 8 - 10⁶ (kg/kmol)

- hydrolysis rate: 10 (%);

- active substance content: 42.0 (%).

The compositions were feed on a roller in the order indicated in Table 4 and were processed for 15 ... 20 minutes, resulting sheets that were calendered at a thickness of 2 ... 3 (mm).

The following data concerning the curing times that are presented in Table 5 where obtained from the rheological characterization of samples of the produced sheets, at temperatures of 160°(C).

Table 4 Compositions used for manufacturing auto mats containing activated mineral batches according to the invention

Table 5 Technological processing times, for the produced mixtures, determined at temperatures of 160° (C)

Curing the sheets in the steam heated press, at temperatures of 150 (°C),at equivalent vulcanization times, auto mats were produced in the mould, that were physico-mechanically characterized, the values presented in Table 6 being obtained.

Table 6 Physico-mechanical characteristics of the produced auto mats

It is noticed that the cured products obtained from the mixture versions T.,, T₂ respectively have the main physico-chemical characteristics superior to those obtained for the mixture version T_n.

Example 3

The elastomeric compositions used for manufacturing technical articles by curing, that are indicated in the Table 7, are dosed. The composition M₀ is the blank assay, in relation to which the comparison is made. Table 7 Elastomeric compositions containing polymeric hydrogels

- average molecular weight: 8 - 10⁶ (kg/kmol)

- hydrolysis rate: 10 (%);

- active substance content: 42.0 (%).

The compositions were feed for processing on a roller in the order indicated in Table 7 and were processed for 15 ... 20 minutes, resulting sheets, that were calendered at a thickness of 2 ... 3 (mm).

The following data concerning the curing times that are presented in Table 8 where obtained from the rheological characterization of samples of the produced sheets, at the temperature of 160°(C). Table 8 Main rheological characteristics, for the produced mixtures, determined at the temperature of 160° (C)

Curing the sheets at equivalent vulcanization times at the temperature of 150°C, cured sheets were produced at the electrical press, in the mould, at a operation pressure acting over the mould of 240 (daN/cm²).

The resulted products were characterized from the physico-mechanical point of view, the values presented in Table 9 being obtained.

Table 9 The main physico-mechanical characteristics of the produced cured sheets

Example 4

The compositions used for manufacturing technical articles by curing, that are indicated in the Table 10, are dosed. The composition T₀ is the blank assay, in relation o which the comparison is made.

Table 10 Elastomeric compositions containing polymeric hydrogels from the class of polyacrylamides

- average molecular weight: 8 - 10⁶ (kg/kmol)

- hydrolysis rate: 10 (%);

- active substance content: 42.0 (%).

The compositions were feed on a roller in the order indicated in Table 10 and were processed for 15 ... 20 minutes, resulting sheets that were calendered at a thickness of 2 ... 3 (mm).

The following data concerning the curing times that are presented in Table 11 where obtained from the rheological characterization of samples of the produced sheets, at the temperature of 160°(C). Table 11 Technological processing times, for the produced mixtures, determined at the temperature of 160° (C)

No. Characteristic U.M. Mixture version

T_n τ₁ T, T,

1. Pre-vulcanization time mm., sec. 2'20" 3'50" 3'30' 4'15'^: 2. Optimum vulcanization time min., sec. 26'15" 12'15" 19' 25' 3. Vulcanization velocity sec^" 4.2 11.9 6.4 4.8

Curing the sheets in the mould, at the electrical press at the temperature of 160 (°C) and acting over the mould with a pressure of 200 (daN/cm²), cured sheets were produced, that were characterized, after relaxation, from the physico-mechanical point of view, the values presented in Table 12 being obtained.

Table 12 The main physico-mechanical characteristics of the produced cured sheets

Example 5

The compositions used for manufacturing cured elastomer sheets, that are indicated in the Table 13, are dosed.

The composition N₀ is the blank assay, in relation to which the comparison is made.

The polymeric hydrogel used is a polyacrylamide derivative which has the ι: following main characteristics:

- average molecular weight: 10⁷ (kg/kmol)

- hydrolysis rate: 20 (%);

- active substance content: 75 (%).

The compositions are processed in a blender for 5 ... 15 minutes, the replenishment with accelerators is made on the roller for 5 ... 15 minutes, resulting sheets that were calendered at a thickness of 1 ... 10 (mm).

The following data concerning the curing times that are presented in Table 14 where obtained from the rheological characterization of samples of the produced sheets, at the temperature of 160°(C).

Curing the sheets at times equivalent to the optimum vulcanization times, on the Auma type continuous process vulcanizer at a operation pressure of 100 ... 600 (daN/cm²) and a operation steam compression of 2 ... 8 (kgf/cm²), and a stationary time of 1 ... 30 (minutes) mat type cured sheets, having widths of 1...2 (m), were produced.

The resulted products were physico-mechanically characterized, the main values presented in Table 15 being obtained.

Table 13 Elastomeric compositions used for manufacturing cured sheets

Table 14 Rheologic characteristics, for the produced mixtures, determined at the temperature of 160° (C)

Table 15 The main physico-mechanical characteristics of the produced cured sheets

Example 6

The polymeric compositions used for producing film forming material for manufacturing barges, mats and raincoats, compositions that are indicated in the Table 16, are dosed. Table 16 Polymeric compositions used for producing film forming material

The polymeric hydrogel used is a polyacrylamide derivative which has the following main characteristics:

- average molecular weight: 8 10⁶ (kg/kmol)

- hydrolysis rate: 10 (%);

- active substance content: 48 (%).

The polymeric compositions are processed in a blender for 10 ... 20 minutes, afterwards they were replenished with vulcanization accelerators on the roller, resulting mixture pieces that were stripped, by calendering, on a polyester fabric, rubber-coated with polychloroprene rubber for adhesion, the film-covered fabric having a width of 1 ... 1.8 (m) .

The rheologic characteristics determined at a temperature of 160 (°C) for the produced polymeric compositions are presented in Table 17.

Table 17 Rheologic characteristics, for the produced mixtures, determined at the temperature of 160° (C)

The film-covered fabrics were cured in the autoclave at a coil steam compression of 4.0 ... 4.5 (bar) at vulcanization times equivalent to the optimum vulcanization times.

The main physico-mechanical characteristics of the produced film-covered fabrics are presented in the Table 18. Table 18 Main physico-mechanical characteristics of the produced film-covered fabrics

Example 7

The polymeric compositions for curing-producing elastic articles ( collars and rosettes for pneumatic boats, tyre components, roller tracks), compositions that are presented in Table 19, are dosed.

- average molecular weight: 8 10⁶ (kg/kmol)

- hydrolysis rate: 15 (%);

- active substance content: 60 (%). Table 19 Compositions used for manufacturing elastic articles

The polymeric compositions were processed on the roller for 15-30 minutes, after which they were sheeted, sheets that were rheolσgically characterized at the temperature of 160 (°C), the results obtained being presented in the Table 20. The composition V₀ is the blank assay. Table 20 Rheologic characteristics, for the produced mixtures, determined at the temperature of 160° (C)

From the produced mixtures, different articles were cured (handles, rosettes, etc.) in the press feed with steam at a pressure of 4.5 (bar), in the mould, at equivalent vulcanization times, depending on the maximal thickness of the article, that was between 2... 54 (mm). The products thus obtained have been physico-mechanically characterized, the main data obtained being presented in the Table 21.

Table 21 The main characteristics of the produced articles

Example 8

The polymeric compositions used for manufacturing auto roller tracks by curing, compositions that are presented in Table 22, are dosed.

Table 22 Compositions used for manufacturing auto roller tracks

The polymeric hydrogel used is of polyacrylamide type which has the following main characteristics:

- average molecular weight: 10⁵ (kg/kmol)

- hydrolysis rate: 0 (%);

- viscosity at 20 (°C): 150±20 (cP) - active substance content: 10 (%).

After obtaining the mixtures in the blender, these were Theologically characterized at the temperature of 160(°C), the obtained results being presented in Table 23.

Table 23 Rheologic characteristics, for the produced mixtures, determined at the temperature of 160° (C)

From the obtained mixtures auto roller tracks were manufactured - at equivalent vulcanization times- at the same work temperature, in moulds. The resulted products were physico-mechanically characterized, the main characteristics obtained being presented in Table 24.

Table 24 Main characteristics of the produced auto tracks

Bibliography

1. - RO patent no. 86811

2. - RO patent no. 88827

3. - RO patent no. 88831 - Sisteme de vulcanizare pentru elastomeri acrilici

4. - RO patent no. 101438 - Sisteme de acceleratori pentru vulcanizarea cauciucului

5. - RO patent no. 69583 - Procedeu pentru prepararea unor amestecuri de cauciuc pulverulente cu proprietati de curgere libera

6. - RO patent no. 100186 - Compozitii din cauciuc compact pentru talpi usoare si procedeu de obtinere a acestuia.

7. - RO patent no. 105209 - Compozitie pe baza de cauciuc microcelular pentru talpa si procedeu pentru obtinerea acesteia.

8. - Caoutchoucs & Plastiques, no. 777, May 1999, pg. 95-99, G. Eward, A. Belgrine et F. Carpier (LR CCP), E. Valot et P. Dang (ATOCHEM)- "Des poudres polyamide utilisees comme renfort".

9. - Zilberman E. N. and co., Vysohomal, Soed. A., 19, 2714, 1977.

Claims

1. Curable elastomeric compositions, characterized in that they are made of: 100 parts per weight elastomers, synthetical and/or natural, up to 240 parts per weight mineral batches (such as calcium carbonate, silicon dioxide, aluminum silicates or combinations thereof); 0.1 ... 5 parts per weight zinc oxide; 0.1 ... 4 parts per weight stearic acid; up to 10 parts per weight resins ( such as colophon, highly styrene resins or coumarone indene resins or combinations thereof); up to 4 parts per weight antioxidants ( such as phenol styrenate, phenyl-β-naphthyl amine or combinations thereof); up to 240 parts per weight carbon black (impingement, furnace, synthesis, from hydrocarbons or combinations thereof); up to 100 parts per weight plasticizer (such as mineral oils, grease, paraffin, dioctyl-phthalate, dioctyl-adipate, dioctyl- sebacate or combinations thereof); up to 50 parts per weight cured caoutchouc powder; up to 4 parts per weight sulphur; 0.1 ... 5 parts per weight vulcanization accelerators ( for example mercaptobenzothiazole, tetramethyl-tiuram-disulphide, N-cyclohexyl- benzothiazyl-2-sulphenamide, diphenylguanidine, benzothiazyl disulphide or combinations thereof); 0.1 ... 240 parts per weight polymeric hydrogel from the class of polyacrylamides, in liquid or/and solid shape, having the following characteristics:

- average molecular weight: 2 10⁴ ... 5 10⁷ (kg/kmol):

- hydrolysis rate: 0 ... 100 (%);

- active dry substance content: 10 ... 75 {%).

2. Curable elastomeric compositions according to claim 1 , characterized in that the elastomer is the natural rubber.

3. Curable elastomeric compositions according to claim 1 , characterized in that the elastomer is of polyisoprene type.

4. Curable elastomeric compositions according to claim 1 , characterized in that the elastomer is of polyacrylonitrile-butadiene type, having a polybutadiene weight percentage between 0.1 ... 100 (%) parts per weight.

5. Curable elastomeric compositions according to claim 1 , characterized in that the elastomer is of ethylene-propylene-diene type, having a ethylene weight percentage between 0.1 ... 100 (%) parts per weight, a propylene weight percentage between 0.1 ... 100 (%) parts per weight and a diene weight percentage between 0.1 ... 100 (%) parts per weight.

6. Curable elastomeric compositions according to claim 1 , characterized in that the elastomer is of butadiene type.

7. Curable elastomeric compositions according to claim 1 , characterized in that the elastomer consists of mixtures of synthetical and/or natural elastomers mentioned in the claims 2, 3, 4, 5 and 6 in parts per weight between 0.01 ... 100 (%).

8. Curable elastomeric compositions according to claim 1 , characterized in that the elastomer is of butadiene-styrene type.

9. Curable elastomeric compositions according to claim 1 , characterized in that they are used for manufacturing rubber or rubber containing technical articles and staple products.