FIBRE-BASED SUPPORT CONTAINING A LAYER OF A FUNCTIONALIZED WATER-SOLUBLE POLYMER, METHOD OF PRODUCTION AND USE THEREOF

Abstract

A method for producing a cellulose and/or synthetic fibre-based support of which at least one surface is coated with a layer containing at least one water-soluble polymer comprising: hydroxyl or primary-secondary amino functional groups, at least some of which have been functionalized beforehand with at least one organic compound comprising at least one epoxy functional group, and at least one R.sup.1 group wherein R.sup.1 is a vinyl functional group or at least one Si(R.sup.2).sub.3 functional group and wherein R.sup.2=hydrogen atom, hydroxyl, alkoxy, alkyl, and combinations thereof.

Claims

1. A method for producing a cellulose and/or synthetic fibre based support comprising at least one surface coated with a layer containing at least one water-soluble polymer comprising hydroxyl or primary-secondary amino functional groups, wherein the method comprises the steps of: (a) forming a cellulose and/or synthetic fibre-based sheet with or without a parchementizing process, (b) prefunctionalizing in water as solvent at least one water-soluble polymer comprising hydroxyl or primary-secondary amino functional groups by grafting at least one organic molecule comprising at least one epoxy group and at least one R.sup.1 functional group wherein R.sup.1 is selected from the group consisting of a vinyl group, and at least one —Si(R.sup.2).sub.3 functional group, wherein R.sup.2=hydrogen atom, hydroxyl, alkoxy, alkyl, and combinations thereof to thereby obtain a prefunctionalized water-soluble polymer; (c) coating the cellulose and/or synthetic fibre-based support with the prefunctionalized water-soluble polymer obtained in step (b); and (d) optionally calendering or supercalendering the support.

2. The method as recited in claim 1, wherein the coating of the cellulose and/or synthetic fibre-based support according to step (c) is carried out at a temperature between 20 and 95° C.

3. The method as recited in claim 1, wherein the water-soluble polymer is functionalized according to step (b) at a temperature between 20 and 95° C., in an aqueous medium and eventually in the presence of an organic or inorganic acid or base.

4. The method as recited in claim 1, wherein the coating techniques include size-press, metering-size-press, foulard coating, rod coating, “Champion” bar coating, “Meyer” bar coating, air-knife coating, gravure coating, scraper blade coating, sliding blade coating, single- and multilayer curtain coating, reverse roll coating, spray coating, atomisation coating, liquid application system (LAS) coating, kiss coating, foam coating, and any surface coating application process.

5. The method as recited in claim 1, wherein the coating of the cellulose and/or synthetic fibre-based support according to step (c) is carried out at a temperature between 20 and 95° C.

6. The method as recited in claim 3, wherein the water-soluble polymer is functionalized according to step (b) at a temperature between 80 and 95° C.

7. The method as recited in claim 5, wherein the coating of the cellulose and/or synthetic fibre-based support according to step (c) is carried out at a temperature between at 50 and 70° C.

8. A cellulose and/or synthetic fibre-based support comprising at least one surface coated with a layer containing at least one water-soluble polymer comprising hydroxyl or primary-secondary amino functional groups which is obtained by the method of claim 1.

Description

EXEMPLARY EMBODIMENTS OF THE INVENTION

[0097] The invention itself and the advantages that it offers will be explained in greater detail in the following description of exemplary embodiments and with reference to the following figures.

[0098] FIG. 1 represents the alkylation reaction, in an aqueous medium at a basic or acid pH, between a water soluble polymer containing hydroxyl functionalities and an organic molecule comprising both an epoxy function and a functional group among, for instance, Si—H, Si—OH, or vinyl. In this particular case, starch is the water soluble polymer containing hydroxyl functionalities while the molecule having an epoxy functionality refers to the general formula: H.sub.2C—O—CH—(R)—R.sup.1.

[0099] FIG. 2 represents the alkylation reaction, in an aqueous medium at a basic or acid pH, between a water soluble polymer containing primary and/or secondary amino functionalities and an organic molecule comprising both art epoxy function and a functional group among, for instance, Si—H, Si—OH, or vinyl. In this particular case, polyethyleneimine is the water soluble polymer containing primary and secondary amino functionality while the molecule having an epoxy functionality refers to the general formula: H.sub.2C—O—CH—(R)—R.sup.1.

EXEMPLES

[0100] Method for Preparing the Glassine According to the Invention:

[0101] A sheet consisting of 100% cellulose fibres is prepared by methods known to one skilled in the art. The support used in the examples is the commercial product Silca Classic Yellow 59 g/m.sup.2 (from Ahlstrom); for the production of the samples described in the examples, the support has not been coated with the standard formulation but with the formulations reported in the examples 1 and 2. In the case of the standard paper, the commercial grade Silca Classic Yellow has been used as such.

[0102] Off-line from the industrial machine, the water soluble polymer containing primary-secondary amino or hydroxyl functionalities is functionalized with an organic molecule by using the methods of examples 1 and 2. After the functionalization reaction, the polymer solution can be mixed with other products commonly used in this application (for example: clays, pigments, latexes, polymers and/or additives), diluted with water to the desired solid content and sent to the industrial machine for the coating step.

[0103] The mixture containing the functionalized water soluble polymer is then applied to a surface of the support by coating (1 g/m.sup.2), preferably by metering-size-press.

[0104] The support is then dried, remoisturized, and super-calandered.

Example 1

Functionalization Reaction of a Water Soluble Polymer Containing Primary and/or Secondary Amino Functionalities and Preparation of the Coating Recipe

[0105] In the present example, polyethyleneimine is the polymer containing primary and/or secondary amino functionalities since it contains both functionalities on the same polymer structure.

[0106] The commercial polyethyleneimine Polymin P (from Basf) is delivered as a water solution with a solid content of 50% w/w. In order to decrease the viscosity of the solution, Polymin P is diluted with water at a solid content of 20%. For the grafting reaction, an amount of 2% w/w of pure 1,2-epoxy-9-decene (from Sigma-Aldrich), compared to the weight of dry Polymin F, is slowly added to the polymer solution under vigorous stirring. The organic molecule 1,2-epoxy-9-decene is a liquid which is not soluble in water, so a vortex is required to create an emulsion of 1,2-epoxy-9-decene in the polymer solution, forming a cloudy solution. Due to the fact that Polymin P in solution already has a pH between 11 and 13, the addition of a base in order to increase the pH to catalyze the reaction is not required. The solution is heated to 90° C. and mainained at this temperature under stirring for one hour. Subsequently, the pH of the solution is neutralized by addition of a water solution of sulphuric acid.

[0107] Afterwards, 20% w/w of CMC and 5% w/w of glyoxal compared to the weight of Polymin P are added to the solution. The solution is then diluted with water to a final solid content of 8% w/w. Finally, the solution is transfered to the coating apparatus for the coating step. CMC is added in the coating formulation as a viscosity modifier to improve the film forming properties and the water retention of the coating formulation. Glyoxal is added as a cross-linking agent for the coating formulation.

Example 2

Functionalization Reaction of a Water Soluble Polymer Containing Hydroxyl Functionalities and Preparation of the Coating Recipe

[0108] In the present example, PVA, Celvol 20/99 (Celanese), is the representative polymer containing hydroxyl functionalities. Celvol 20/99 is delivered as a powder. A dispersion of PVA is produced in water by vigorous stirring. It is then heated up to 95° C. in order to completely dissolve PVA in water. A clear solution with a solid content of 12% is obtained. A solution of sodium hydroxide is added to the PVA solution in order to reach a pH value between 11 and 13. For the grafting reaction, an amount of 2.5% w/w of pure 1,2-epoxy-9-decene (from Sigma-Aldrich), compared to the weight of dry Polymin P, is slowly added to the polymer solution under vigorous stirring. The organic molecule 1,2-epoxy-9-decene is a liquid which is not soluble in water, so a vortex is required to create an emulsion of 1,2-epoxy-9-decene in the polymer solution, forming a cloudy solution. The solution is heated to 90° C. and mainained at this temperature under stirring condition for three hours. Subsequently, the pH of the solution is neutralized by addition of a water solution of sulphuric acid. Afterwards, 10% w/w of CMC and 5% w/w of glyoxal compared to the weight of PVA are added to solution. The solution is then diluted with water to afford a final solid content of 8% w/w. Finally, the solution is transfered to the coating apparatus for the coating step.

Example 3

Silicone Anchorage of Low Temperature Curing (LTC) Silicone Systems

[0109] Standard glassine (STD) and the glassine produced by the methods reported in examples 1 (EX1) and 2 (EX2) have been siliconized with LTC silicones. The silicone anchorage results have been compared. In order to assess the silicone anchorage, a standard test called rub-off test has been perforated; this test is an abrasion test in which a sample of siliconized paper, pressed under a weight, is dragged on an abrasive textile. The silicone layer at the surface of the sample can be removed by the rubbing. By measuring the amout of silicone onto the samples before and after the rubb-off test, it is possible to obtain a percentage of silicone that remains on the samples. The rub-off percentage 0% indicates that all the silicone has been removed from the sample, very poor adhesion; the rubb-off percentage 100% indicates that all the silicone remained on the sample, the adhesion is ideal. For the release application, the rub-off value of 75% is commonly considered as the bottom limit for silicone ancohorage. The following silicone formulation has been used in this example:

[0110] LTC silicone formulation bath:

[0111] Polymer: D920 (from Wacker)—18.07 g

[0112] Cross-linking agent: XV 525 (from Wacker)—1.43 g

[0113] Catalyst: C05 (i.e.: Platinum based from Wacker)—2.14 g

[0114] Deposit: 0.9 g/m.sup.2

[0115] Cross-linking for 30 seconds at 80° C. in a ventilated drying kiln

[0116] Table 1 shows that STD has a rub-off value of 18% (very poor adhesion of the silicone), whereas EX1 and EX2 have respectively rub-off values of 96% and 97% (both samples have very good adhesion properties for LTC silicone systems). So, in the case of standard glassine the LTC silicone cannot be used due to the poor adhesion of the silicone system to the substrate; on the contrary, LTC silicone systems can be used on glassine produced by the methods reported in the present invention.

TABLE-US-00001 TABLE 1 Sample STD EX1 EX2 Rub-off value 18% 96% 97%

Example 4

Silicone Anchorage Dependence on the Amount of Catalyst (i.e.: Platinum) in the Silicone Formulation

[0117] For thermal cured silicone systems used in release industry, the catalyst used is an organometallic compound of platinum. Due to the high price of platinum, there is a strong interest in reducing its amount in the silicone formulation. The first problem observed when a reduced amount of catalyst is used is a poor anchorage of the silicone to the substrate.

[0118] Standard glassine (STD) and the glassine produced by the methods reported in examples 1 (EX1) and 2 (EX2) have been siliconized with a standard silicone formulation by using two different amounts of catalyst in the silicone formulation, and the silicone anchorage on different substrates has been tested. In order to evaluate the silicone anchorage, the rub-off test (described in example 3) has been performed. For the tests the following silicone formulations have been used:

[0119] Standard silicone formulation bath:

[0120] Polymer: 11.367 (from Bluestar) 50 g

[0121] Cross-linking agent: 12031 (from Bluestar)—2.9 g

[0122] Catalyst (60 ppm Platinum): 12070 (from Bluestar) 1.56 g; or (30 ppm Platinum): 12070—0.78 g

[0123] Deposit: 0.9 g/m.sup.2

[0124] Cross-linking for 10 seconds at 160° C. in ventilated drying kiln

[0125] As it is possible to observe in table 2, an satisfactory rate of silicone anchorage is obtained for all samples when the silicone formulation contains 60 ppm of platinum. On the contrary, when the amount of platinum is decreased to 30 ppm, the silicone anchorage of samples EX1 and EX2 remains very good but the anchorage of STD is poor.

TABLE-US-00002 TABLE 2 STD EX1 EX2 Rub-off 90% 95% 98% (60 ppm of Platinum) Rub-off 54% 91% 93% (30 ppm of Platinum)