JPH0457997A - Manufacture of sheet - Google Patents

Abstract

PURPOSE:To obtain a sheet composed mainly of an inorganic filler and suitable for building materials or for flame-retardant or non-flammable use by adding a specific anionic polyacrylamide and a fixing agent and using bentonite as a flocculant. CONSTITUTION:A sheet is produced from a paper material composed mainly of an inorganic filler by adding (A) an anionic polyacrylamide having a molecular weight of 300,000-1,000,000 and (B) a fixing agent for the component A (preferably polyamide polyamine epichlorohydrin, a cationized starch and/or aluminum sulfate) to the filler and using (C) bentonite as a flocculant.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for making sheets for use as building materials or for uses requiring flame retardancy and non-combustibility.

(Prior art) When making a sheet from a paper stock containing mainly inorganic fillers, generally containing inorganic fillers in the range of 60 to 90% by weight of the solid content, there are problems with the strength of the sheet and the fixation of the filler. becomes. As a countermeasure to this problem, a method is generally used in which latex is used as an internal binder and a flocculant or colloid destabilizing agent is used to improve the yield.

(Problems to be solved by the invention) However, in the method of internally adding latex, the latex tends to stain the piping and the inside of the chest, and also in paper machines, lees accumulate on wire felt, rolls, canvas, dryers, etc. It is easy for lees to get mixed in and holes to occur. Therefore, it is necessary to perform frequent cleaning and install equipment to prevent the generation of lees and dirt. If a sheet with further strength is required, the rate of latex addition must be increased. As a result, the cost increases and the sheet becomes easily flammable.

Further, in this method, there remains the problem that if the amount of coagulant added is increased in order to increase the yield of filler, the texture of the sheet deteriorates.

(Means for Solving the Problems) The present inventors have made extensive studies to overcome these drawbacks and have completed the present invention. The present invention provides (1) molecular weight of 300,000 to 100
This is a method of making a sheet from a paper stock mainly containing an inorganic filler by using (2) internally adding a fixing agent for the polyacrylamide, and (3) using bentonite as a flocculant.

The polyacrylamide used in the present invention has a molecular weight of 11.3 million to 10
00,000 anionic polyacrylamide. The amount of anionic polyacrylamide added depends on the filler, type of fiber,
Since it depends on the formulation, it is not possible to make a general statement, but it is generally sufficient to use 1 to 5 parts by weight based on 100 parts by weight of the filler and fibers. As the amount added increases, the flame retardancy of the sheet decreases. A cationic fixing agent is used to fix this polyacrylamide to the paper stock. The fixing agent is not particularly limited, but it is preferable to use one or more selected from polyamide polyamine shrimp chlorohydrin, cationic starch, and sulfuric acid. If a sheet that maintains wet strength is required, polyamide polyamine shrimp chlorohydrin may be used alone or in combination. The amount of the cationic fixing agent to be added depends on the anionic polyacrylamide used, so it is difficult to say exactly, but it is generally from 30 to 150 parts by weight per 100 parts by weight of the anionic polyacrylamide.

Bentonite is added in an amount of 0.1 to 1.0 parts by weight per 100 parts by weight of the solid content of the paper stock thus obtained.

Bentonite is dispersed in rough water, for example 0.1~
A 3.0% by weight aqueous dispersion is prepared and introduced at one or more locations in the machine chest, before the fan pump, before the screen, or after the screen.

Since the paper stock prepared in this manner does not use latex, the sheet obtained without contaminating the stock supply system and the papermaking process retains strength and has good texture and yield. In order to further increase the yield, high molecular weight polyacrylamide as a flocculant can also be used.

Starch and or PV to improve the surface strength of the sheet
A may be impregnated or coated.

In the present invention, inorganic fillers refer to water-insoluble and non-fibrous inorganic powders such as aluminum hydroxide, magnesium hydroxide, calcium carbonate, talc, titanium dioxide, and pigments. , refers to those in which the inorganic filler is approximately 60 to 90% by weight of the solid content.

Although the second component of the sheet in the present invention is fiber, it may also contain water-dispersible fibers other than valves.

Water-dispersible fibers other than bulbs include glass fibers, synthetic fibers, recycled fibers, ceramic fibers, rock wool fibers, and the like. The amount of fiber in the paper stock varies depending on the amount of filler added, but
It is within the range of 5% by weight, and it is particularly preferable that 50% by weight or more of the fibers be bulbs. It may also contain general paper chemicals.

(Effects of the Invention) According to the present invention, a sheet with good filler yield, high strength, and high flame retardance can be obtained without contaminating the papermaking system even when operated continuously for a long time.

(Example) Specific examples of the present invention are shown below.

Example 1 A paper stock having the composition shown in Table 1 was made using NBKP prepared in this manner at 30°SR. At that time, 0.6 parts by weight of bentonite was added as a flocculant to 100 parts by weight of paper solid content after the screen. Although continuous papermaking was carried out 24 hours a day, there was no contamination of the paper stock supply system or the papermaking process. The physical properties of the sheet are as shown in Table 2, and it is strong and highly flame retardant (JI
A flame retardant grade 2) sheet was obtained using SA1322.

Example 2 A paper stock having the composition shown in Table 1 was made using 25" SR with the above-described NBKP. At that time, 0.4 parts by weight of bentonite was added as a flocculant to 100 parts by weight of the solid content of the paper stock before the fan pump. Furthermore, 0.03 parts by weight of anionic high molecular weight polyacrylamide (molecular weight 6 million) per 100 parts by weight of paper solids was added as a flocculant in front of the screen. Although paper making was continued for 24 hours, the paper stock There was no dirt in the supply system or in the papermaking process.The physical properties of the sheet are as shown in Table 2, and it is strong and highly flame retardant (JIS
A flame retardant grade 1) sheet was obtained using A1322.

Comparative Example 306SR was made into a paper stock having the composition shown in Table 1 using the NBKP prepared in this manner. As a flocculant, 0.05 parts by weight of high molecular weight polyacrylamide (molecular weight 4 million) per 100 parts by weight of paper solids was added in front of the screen. Five hours after the start of papermaking, the dryer and canvas became extremely dirty, and the dirt on the canvas began to transfer to the sheet. For this reason, papermaking was temporarily stopped, the dryer and canvas were cleaned, and papermaking was restarted. The paper-making process was continued for 24 hours by repeating such stoppage. After papermaking was completed, lumps of paper stock were attached to the paper stock supply system, and the cleaning time was 50% longer than when latex was not used. The physical properties of the sheet were as shown in Table 2, and the strength was low despite the high addition rate of paper strength agent.

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Claims (1)

[Scope of Claims] 1. In making a sheet from a paper stock mainly containing an inorganic filler, (1) an anionic polyacrylamide with a molecular weight of 300,000 to 1,000,000 and (2) a fixing agent for the polyacrylamide are internally added. (3) A sheet manufacturing method characterized by using bentonite as a flocculant. 2. The method for making a sheet according to claim 1, wherein the fixing agent for polyacrylamide is one or more selected from polyamide polyamine epichlorohydrin, cationic starch, and sulfuric acid.