JPS595704B2 - Manufacturing method of waterproof sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a waterproof sheet with excellent durability.

Conventionally, as a method of applying a highly durable waterproofing treatment to paper fabric, an emulsion of an initial condensate of polysiloxane is applied to the paper fabric, and after preliminary drying, it is heated at a temperature of 150 to 160°C for 3 to 30 minutes.
A method of baking for 5 minutes is known.

However, in this method, polysiloxane (generally
Methylhydrodiene polysiloxane is used. )
Since the polymer itself forms a three-dimensional structure on the paper fabric, the texture of the paper fabric is impaired, and perfect durability is not necessarily obtained. On the other hand, methods of grafting various monomers onto paper cloth are also known, but in the conventional method of grafting onto paper cloth, free radicals are generated in cellulose by exposing the paper cloth to radiation such as electron beams. The paper cloth is then immersed in a solution or dispersion of the monomer, which has the disadvantage of requiring a large and complex reaction apparatus.

Furthermore, this method has the disadvantage that the reaction must be carried out in an atmosphere of inert gas or in a vacuum, since radicals generated by radiation irradiation combine with oxygen in an atmosphere of oxygen.

The inventors of the present invention conducted research to solve these conventional difficulties, and found that a paper cloth made of cellulose fibers was immersed in a silanol condensation catalyst bath, and then the paper cloth was placed in an atmosphere of vinyltrialkoxysilane. In this case, it was discovered that vinyltrialkoxysilane undergoes a grafting reaction on paper fabric, imparting durability and excellent water repellency to the paper fabric surface.

The present invention has been made based on this knowledge, and is a waterproofing method characterized by grafting vinyltrialkoxysilane to a paper cloth made of cellulose fibers containing a silanol condensation catalyst in the gas phase. The first invention relates to a method for producing a synthetic sheet, and in carrying out the first invention, a silicone-grafted synthetic resin film is applied to the paper cloth made of cellulose fibers before or after the grafting reaction. The second invention relates to a method for manufacturing a waterproof sheet, which is characterized in that the silicone-grafted synthetic resin film is laminated and fused and then hydrolyzed and crosslinked in the presence of a silanol condensation catalyst.

Paper cloths made of cellulose fibers used in the first invention include kraft paper, condenser paper, cotton cloth, linen cloth, rayon cloth, and the like.

However, if necessary, it is also possible to replace up to 80If6 with synthetic fibers or other non-cellulose fibers to use a paper fabric made of a mixed paper or a blended material. Examples of silanol condensation catalysts include dibutyltin dilaurate and dibutyltin diacetate, and examples of vinyltrialkoxysilanes include vinyltrimethoxysilane and vinyltriethoxysilane.

The first invention is carried out, for example, by two methods: a continuous processing method and a batch processing method, which will be described below.

Regarding the continuous processing method, as shown in FIG. 1, kraft paper 1 that is continuously fed out is immersed in a catalyst bath 2 in which, for example, dibutyltin dilaurate is dissolved in an organic solvent such as methanol or acetone. After the solvent is volatilized by the heating device 3, it is introduced into a reaction vessel 4 filled with vinyltrimethoxysilane vapor and heated to 60 to 110°C.
The action of dibutyltin dilaurate supported on the surface causes the following silane coupling reaction with vinyltrimethoxysilane to produce water-repellent silyl groups on the surface.

Alternatively, instead of immersing the kraft paper 1 in the catalyst bath 2, the silane coupling reaction can be carried out by allowing dibutyltin dilaurate vapor to coexist in the reaction vessel 4.

On the other hand, in the batch processing method, as shown in Fig. 1, the kraft paper is passed through a heating device 3 to volatilize the solvent and is once wound onto a reel, and then this reel is placed in a reaction vessel. The silane coupling reaction is carried out by filling with vinyltrimethoxylan vapor.

The silicone grafted synthetic resin film used in the second invention is manufactured as follows.

That is, first, preferably 0.01 to 2.0% by weight of a radical generator such as dicumyl peroxide DCP and vinyl trimethoxy are added to an organic polymer such as high density, medium density or low density polyethylene or polypropylene. Compounds with hydrolyzable silyl groups such as silane VTMOS and vinyltriethoxysilane VTEOS
5.0% by weight, and then supplied to a device having a heating kneading function such as an extruder, to give about 20% by weight.
It is obtained by heating and kneading at 0°C. At the stage when most of the silane compound has reacted, this silicone-grafted synthetic resin is usually pelletized. The silicone grafted human + Ayumi-1-... obtained in this way
A masterbatch containing a silanol condensation catalyst such as 1-1-dipty-4 diacetate is added and mixed;
It is formed into a film by the T-die method or the inflation method. The silanol condensation catalyst may be added to the organic polymer together with the silane compound, radical generator, etc. prior to the grafting reaction of the silane compound. However, the second invention is, as shown in FIG. A film 7 of a synthetic resin having a hydrolyzable silyl group, such as a silicone-grafted polyolefin, containing a condensation catalyst, is laminated with paper cloth 8, 8' on which vinyltrialkoxysilane is grafted by a silane coupling reaction. This is carried out by heating and pressurizing the film with a heating roll 9 to fuse them together, and then crosslinking the film with water.

Incidentally, the grafting of the alkoxysilane onto the paper cloths 8, 8' may be carried out after the film 7 and the paper cloths 8, 8' are fused together. Alternatively, paper cloth may be laminated only on one side of the film 1. Furthermore, in the above examples, the silanol condensation catalyst was added as a masterbatch at the time of film extrusion, but the film was formed without adding the silanol condensation catalyst, and then laminated with paper cloth carrying the silanol condensation catalyst. Alternatively, the hesilanol condensation catalyst may be transferred from the surface into the film to crosslink the film.

The waterproof sheet obtained by the first invention has excellent durability because the vinyltrialkoxysilane is directly grafted onto the paper fabric. The waterproof sheet obtained by the first invention is further laminated with a synthetic resin sheet, so it has moisture resistance and exhibits excellent mechanical strength and heat resistance. .

The waterproof sheets obtained according to the first invention and the second invention are suitable for various uses such as jets, car body covers, general-purpose waterproof sheets, rain cover fabrics, warm water sheets, agricultural sheets, etc. Paper 1 has particularly excellent electrical properties and is therefore suitable as electrical insulating paper for various oil-immersed electrical devices or windings.

It can be applied to a wide range of other uses requiring waterproofness and heat resistance (120°C or less). Next, examples will be described. Example 1 In the previous step of the method shown in Figure 1, kraft paper with a thickness of 40 μm was impregnated with a solution of 0.2 parts by weight of dibutyltin dilaurate and 100 parts by weight of acetone, and the acetone was evaporated to make the cotton. The cloth was wound onto the take-up reel.

Next, this reel was placed in a liquid state in a 5 t sealed reaction vessel filled with 20 cc of vinyltrimethoxysilane vapor, and left at 80° C. for 24 hours to carry out a silane coupling reaction. The thus-balled silicone-grafted kraft paper was extracted three times for 8 hours using a Soxle extractor, and the grafting rate was measured after vacuum drying.

The grafting rate of this silicone-grafted kraft paper was about 2.3%.

Example 2 Using the silicone grafted kraft paper obtained in Example 1, a laminate sheet was manufactured by the method shown in FIG.

The structure of the obtained laminate sheet is silicone-grafted kraft paper - silicone-grafted polyethylene -
Silicone grafted kraft paper = 50μm40μm5
When the peel strength between the layers was measured after the silicone-grafted polyethylene was crosslinked by being left indoors overnight, it was found to have a peel strength higher than the breaking strength of the silicone-grafted kraft paper.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the first invention, and FIG. 2 is an explanatory diagram showing the second invention. 1...Kraft paper, 2...Catalyst bath, 3
... Heating device, 4 ... Reaction container, 5.
... Extruder, 6 ... Head having a T-die, 7 ... Film having a hydrolyzable silyl group, 8,85 ... Paper cloth, 9...●●●Heating mouth rill.

Claims (1)

[Scope of Claims] 1. A method for producing a waterproof sheet, which comprises carrying out a grafting reaction of vinyltrialkoxysilane in a gas phase onto a paper cloth made of cellulose fibers carrying a silanol condensation catalyst. 2. The method for producing a waterproof sheet according to claim 1, wherein the grafting reaction is carried out at a temperature of 60 to 120°C. 3. The method for producing a waterproof sheet according to claim 1 or 2, wherein the vinyltrialkoxysilane is vinyltrimethoxysilane. 4. The method for producing a waterproof sheet according to any one of claims 1 to 3, wherein the silanol condensation catalyst is dibutyltin dilaurate. 5. When grafting vinyltrialkoxysilane to a paper cloth made of cellulose fibers supporting a silanol condensation catalyst in the gas phase, the paper cloth made of cellulose fibers is treated with silicone before or after the grafting reaction. A method for producing a waterproof sheet, which comprises laminating and fusing a silicone-grafted synthetic resin film, and hydrolyzing and crosslinking the silicone-grafted synthetic resin film in the presence of a silanol condensation catalyst. 6. The method for producing a waterproof sheet according to claim 5, wherein the silicone-grafted synthetic resin is silicone-grafted polyethylene.