GB1588354A

GB1588354A - Synthetic polymer- or resin-reinforced paper and preparation thereof

Info

Publication number: GB1588354A
Application number: GB3044677A
Authority: GB
Original assignee: Hoechst Gosei KK
Current assignee: Hoechst Gosei KK
Priority date: 1976-07-20
Filing date: 1977-07-20
Publication date: 1981-04-23
Also published as: JPS5314823A; JPS5944439B2

Description

(54) SYNTHETIC POLYMER - OR RESIN-REINFORCED PAPER AND PREPARATION THEREOF (71) We, HOECHST GOSEI KABUSHIKI KAISHA a corporation organised and existing under the laws of Japan of No. 10-33, Akasaka 4-chome, Minato-ku, Tokyo 107, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a synthetic polymer- or resin-reinforced paper having improved properties and to the preparation thereof.

Attempts have been made to improve the quality of paper by the addition of a natural polymeric material such as starch or a starch derivative or a synthetic polymeric material such as an urea resin, a melamine resin, a polyvinyl acetate, a polyacrylate or a polyacrylamide, at various stages in the manufacture of the paper. However, when such an additive is employed, there has been a tendency for the additive to be insufficiently retained on the paper fibers, or for the dry tearing strength of the paper to be lowered, or for the paper to become brittle on storage for lengthy periods of time. Also, when an aqueous emulsion of a synthetic polymer or resin such as a polyvinyl acetate or a polyacrylate is employed without modification, various problems arise. Thus, for instance, the retention of the polymer or resin is poor, the resin tends to stick to the walls of pulp storage tanks and staining of the pick-up felt occurs. Also, at the drying stage, the synthetic polymer or resin adheres to the surface of the dryer due to the stickiness which is characteristic of an emulsion of a synthetic polymer or resin.

We have sought to provide a polymer- or resin-reinforced paper with good properties, and a process for preparing such polymeror resin-reinforced paper in which the above disadvantages are minimised or avoided.

The present invention provides a process for preparing a synthetic polymer, or resinreinforced paper sheet, which comprises adding short fibers normally incapable of forming a paper web and a coagulated polymer or resin slurry obtained by coagulating an emulsion of a synthetic polymer or resin by means of a coagulant to a pulp slurry in a beater, and forming a paper sheet on a paper machine, said short fibers normally incapable of forming a paper web being natural or man-made fibers which can pass through a wire net of 60 to 150 mesh (Tyler).

The polymer- or resin-reinforced paper of the present invention may be prepared by the following three processes: (i) Short fibers normally incapable of forming a paper web and a coagulated resin slurry obtained by coagulating an emulsion of a synthetic resin with the use of a coagulant are added to a pulp slurry in a beater, and a sheet is then formed from the resulting mixture.

(ii) The short fibers and the emulsion are admlxed, and a coagulant is added thereto to coagulate the resin. The resulting coagulated resin-fiber composition is added to a pulp slurry in a beater, and a sheet is then formed from the resulting mixture.

(iii) The short fibers and the emulsion are added to a pulp slurry in a beater and, after coagulating the resin by employing a coagulant, a sheet is formed from the resulting mixture.

The short fibers employed in the present invention may be selected from pulp and other natural fibers, and man-made fibers such as nylon and rayons.

In the present invention, various fine natural and man-made fibers may be employed as the short fibers normally incapable of forming a paper web, the suitable short fibers being those which can pass through a wire net of 60 to 150 mesh Tyler). Therefore, for instance, a pile employed in flocking and a fine pulp which passes through a wire net of a paper machine and exists in the waste water of a paper-making may be satisfacorily employed in the present invention.

Aqueous emulsions of homopolymers and copolymers of cY,pethylenically unsaturated monomers and synthetic rubber latices may be employed as the emulsion of a synthetic polymer or resin in the process of the pres ent invention. Examples of the ex,ss- ethylenically unsaturated monomers include vinyl esters such as vinyl acetate, vinyl propionate and vinyl versatate (commercially available under the registered trade mark of "Veova" and made by Shell Kagaku Kabushiki Kaisha), unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid and maleic acid, alkyl esters of unsaturated acids, styrene and derivatives thereof such as methylstyrene and chlorostyrene, and olefins and haloolefins such as ethylene, propylene and vinyl chloride. The aqueous emulsion may be prepared by emulsiopolymerizing one such monomer alone, or a mixture monomers in an aqueous medium.

The monomers may also be copolymerized with a monomer such as acrylonitrile, acrylamide or dibutyl maleate, or a crosslinking monomer such as N-methylolacrylamide, n-butoxymethylacrylamide, glycidyl methacrylate, diacetone acrylamide, allylmethacrylate or diethylene glycol dimethylacrylate. Examples of a synthetic rubber latex include styrene-butadiene rubber latex, chloroprene rubber latex, nitrile rubber latex and isoprene rubber latex.

According to the present invention, the waste water of a factory in which synthetic polymers or resin emulsions are made and which contain the synthetic polymer or resin may be employed in the process of the invention In the process of the present invention the resin particles in the emulsion are coagulated by employing a coagulant. There are suitably employed as the coagulant in the process of the present invention polyvalent metal salts such as alum, aluminium sulfate, ferric sulfate, ferric chloride, aluminium chloride or polyaluminium chloride, and mixtures of a polyvalent metal salt with a monovalent or bivalent metal hydroxide such as sodium hydroxide, calcium hydroxide or barium hydroxide, and polymeric coagulants such as polyacrylamide and mixtures of the polymeric coagulant with the polyvalent metal salt. The above coagulant may also be employed in combination with a small amount of water-soluble boron compound such as boric acid or borax when a very stable emulsion is used. For instance, in the case of a very stable polyvinyl acetate emulsion stabilized with polyvinyl alcohol, the addition of the water-soluble boron compound, the monovalent or bivalent metal hydroxide and the polyvalent metal salt to the emulsion in that order can make the resin particles in the emulsion coagulate rapidly.

The preferred amount of the watersoluble boron compound employed is from 0.01 to 10% by weight based on the weight of the resin component in the emulsion. The preferred amount of the monovalent or bivalent metal hydroxide employed is from 0.2 to 20% by weight based on the weight of the resin component in the emulsion. The preferred amount of the polyvalent metal salt is from 0.05 to 50% by weight based on the weight of the resin component in the emulsion.

Further, when ferric chloride or ferric sulfate is employed as the polyvalent metal salt in combination with the boron compound and the metal hydroxide, the resulting resin-reinforced paper has an antistatic property.

The process of the present invention has the following advantages: (i) The short fiber is efficiently retained by the coagulated polymer or resin containing the paper-making fiber, since the short fiber has a very good affinity for the coagulated resin in a pulp slurry. Also, the coagulated polymer on resin does not show any stickiness. Thhhe staining of the pick-up felt and the sticking of the resin to the surface of a dryer do not occur, and also the transparency of the white water is very high.

(ii) The resinous material containing the short fiber has an excellent filling effect. The paper obtained is very flexible and strong as compared with the conventional case where calcium carbonate and clay are employed as a filler. Also, abrasion of the wire net of a paper machine decreases. This is a feature which cannot be obtained by the use of a filler such as calcium carbonate or clay.

(iii) The paper obtained exhibits a sizing effect.

(iv) Printing of a pattern such as graining can be made on the paper without any undercoat, and the printed paper can be used as a pattern paper for a decorative board.

(v) The present invention makes it possible to incorporate a large quantity of resin (50 to 200% by weight) into a paper. Therefore, when the paper is thick, it can be moulded by a thermal press.

(vi) Paper having an antistatic property can be obtained by choosing a suitable coagulant, and is applicable to a special use such as a paper to be put between sheet glasses for the purpose of protecting them from possible damage (the paper for this use is hereinafter referred to a a protective paper).

(vii) The waste water of an emulsion factory, and the waste water of paper-making or a sludge obtained from the waste water of paper-making may also be utilized. This is advantageous from the viewpoint of environmental protection or the prevention of environmental pollution.

The present invention is more particularly described and explained by means of the following Examples, in which all percentages are percentages by weight.

Example 1 An emulsion of polyvinyl acetate having a solids concentration of substantially 50% was diluted with water to a 1% solids concentration. 1% of boric acid, 10% of calcium hydroxide and 5% of aluminium chloride, based on the weight of the resin component in the emulsion, were added in that order to the diluted emulsion to coagulate the resin particles, and the supernatant liquid was then removed to give a coagulated resin slurry containing substantially 20% solids.

A pulp consisting mainly of kraft pulp was beaten to 35%SR freeness. The slurry was added to the pulp in a beater in an amount of 150% (calculated as solid matter), based on the dry weight of the pulp. Further, 50% of a nylon pile fiber fineness: 3d (Denier), length: 0.5 mm. based on the dry weight of the pulp, was sufficiently wetted with water, and then added to the pulp in a heater.

After agitating to produce a uniform mix, a sheet was formed employing five vats. The staining of the pick-up felt and the sticking of the resin to the surface of the dryer were not observed. Also, the transparency of the white water was very high.

The resin-reinforced paper obtained showed a highfractiure strength and had a high delamination resistance. Also, thermal press moulding of the paper was possible, and the printing of a pattern such as gaining could be made on the paper without any undercoat as the sizing degree of the paper was high. The flexibility and strength of the resulting paper were superior to those of a paper containing mineral fillers such as calcium carbonate and clay.

Example 2 An emulsion of vinyl acetate-acrylic ester copolymer having a solids concentration of substantially 40% was diluted with water to substantially 2% solids concentration. 10% of aluminium sulfate based on the weight of the resin component in the emulsion was added to the diluted emulsion to coagulate the resin particles, and the supernatant liquid was then removed to give a coagulated resin slurry having a solids content of substantially 10%.

With the resulting slurry, a resinreinforced paper was prepared in the same manner as in Example 1.

The staining of the pick-up felt and the sticking of the resin to the surface of a dryer were not observed, and the transparency of the white water was very high. Also, the quality of the obtained resin-reinforced paper was similar to that of the resinreinforced paper obtained in Example 1.

Example 3 The procedures of Example 1 were repeated. However, a waste water containing 0.1% of solid matter from an emulsion factory (of which the main component was an emulsion of homo- or co-polymers of acrylates, styrene and vinyl acetate, and which further contained emulsifiers such as a surface active agent and a water-soluble polymeric material) was employed instead of the emulsion of polyvinyl acetate diluted to 1% solids concentration. Furthermore, a sludge containing substantially 20% of solid matter (mainly consisting of a pulp of short fibers, a natural or synthetic water-soluble resin and a filler for paper) obtained from the waste water of paper-making was employed instead of the nylon pile.

The quantity of the resin-reinforced paper obtained was similar to that of the resinreinforced paper of Example 1.

Example 4 The same waste water from an emulsion factory as was employed in Example 3 and the same sludge as was employed in Example 3 were admixed with solid matter in a weight ratio of substantially 1:1. To the resulting mixture there waere added 2% of boric acid, 15% of calcium hydroxide and 10% of ferric chloride in that order, based on the weight of the resin components in the waste water, so as to coagulate and to coprecipitate the resin components and the sludge. The resulting slurry contained substantially 20% of solid matter.

The resulting slurry was added to a waste paper stock in a beater in an amount of 100% (calculated as solid matter), based on the dry weight of the waste paper stock, and then a wet paper was formed by employing a Fourdrinier machine in a conventional manner, and dried by a Yankee dryer to give a resin-reinforced paper.

The staining of the pick-up felt and the sticking of the resin to the surface of the dryer were not observed, and the transparency of the white water was very high.

The resin-reinforced paper obtained was very strong, and the printing property of the paper was excellent due to its high degree of sizing. Also, the paper had an antistatic property and, therefore, when it was put between sheet glasses as a protective paper, it could be readily separated from the glass.

Example 5 To a slurry of kraft pulp beaten to 200SR freeness in a beater were added the same sludge as was employed in Example 3 in an amount of 10% ,calculated as solid matter), based on the weight of the kraft pulp, and then an emulsion of vinyl acetate-ethylene copolymer having a solids concentration of 50% in an amount of 5% (calculated as a resin component) based on the weight of the fraft pulp. After uniform mixing, to the resulting mixture there were added 5% of boric acid, 10% of calcium hydroxide and 5% of ferric chloride in that order, based on the weight of the resin component in the emulsion, so to coagulate the resin and the sludge and so to precipitate them onto the kraft pulp. A sheet was formed by a Fourdrinier machine and was dried to give a resin-reinforced paper.

The staining of the pick-up felt and the sticking of the resin to the surface of a dryer were not observed and the transparency of the white water was very high.

The resin-reinforced paper obtained showed a high fracture strngth and the printing property of the paper was excellent due to its high degree of sizing. Also, the paper had an antistatic property and, therefore, when it was put between glass sheets as a protective paper, it could be readily separated from the glass.

WHAT WE CLAIM IS: 1. A process for preparing a synthetic polymer- or resin-reinforced paper sheet, which comprises adding short fibers normally of forming a paper web and a coagulated polymer or resin slurry obtained by coagulating an emulsion of a synthetic polymer or resin by means of a coagulant to a pulp slurry in a beater, and forming a paper sheet on a paper machine, said short fibers normally incapable of forming a paper web being natural or man-made fibers which can pass through a wire net of 60 to 150 mesh (Tyler).

2. A process for preparing a synthetic polymer- or resin-reinforced paper, which comprises adding a coagulated polymerfiber or resin-fiber composition, obtained by admixing short fibers normally incapable of forming a paper web and an emulsion of a synthetic polymer or resin and adding a coagulant to the resulting mixture, to a pulp slurry in a beater, and forming a sheet on a paper machine, said short fibers normally incapable of forming a paper web being natural or man-made fibers which can pass through a wire net of 60 to 150 mesh (Tyler).

3. A process for preparing a synthetic polymer- or resin-reinforced paper as claimed in claim 1 or 2, wherein said coagulant is at least one of polyvalent metal salts, mixtures of polyvalent metal salts with monovalent or bivalent metal hydroxides, and polymeric coagulants.

4. A process for preparing a synthetic polymer- or resin-reinforced paper as claimed in claim 1 or 2, wherein said coagulant is at least one of mixtures of polyvalent metal salts with monovalent metal hydroxides, and polymeric coagulants, and is employed in combination with a small amount of at least one water-soluble boron compound.

5. A process for preparing a resinreinforced paper as claimed in claim 1 or 2, wherein said coagulant is a polyvalent salt employed in combination with a watersoluble boron compound and a monovalent or bivalent metal hydroxide.

6. A process for preparing a polymer- or resin-reinforced paper as claimed in claim 5, wherein said polyvalent metal salt is at least one of ferric chloride and ferric sulphate.

7. A process for preparing a synthetic polymer- or resin-reinforced paper sheet substantially as hereinbefore described with reference to any one of the specific examples.

8. A polymer- or resin-reinforced sheet when prepared by a process as claimed in any of claims 1 to 7.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. emulsion, so to coagulate the resin and the sludge and so to precipitate them onto the kraft pulp. A sheet was formed by a Fourdrinier machine and was dried to give a resin-reinforced paper. The staining of the pick-up felt and the sticking of the resin to the surface of a dryer were not observed and the transparency of the white water was very high. The resin-reinforced paper obtained showed a high fracture strngth and the printing property of the paper was excellent due to its high degree of sizing. Also, the paper had an antistatic property and, therefore, when it was put between glass sheets as a protective paper, it could be readily separated from the glass. WHAT WE CLAIM IS:

1. A process for preparing a synthetic polymer- or resin-reinforced paper sheet, which comprises adding short fibers normally of forming a paper web and a coagulated polymer or resin slurry obtained by coagulating an emulsion of a synthetic polymer or resin by means of a coagulant to a pulp slurry in a beater, and forming a paper sheet on a paper machine, said short fibers normally incapable of forming a paper web being natural or man-made fibers which can pass through a wire net of 60 to 150 mesh (Tyler).