JPH0770980A - Production of flame-retardant paper for paper honeycomb core - Google Patents

Abstract

PURPOSE:To produce flame-retardant paper for paper honeycomb cores consisting of inorganic paper containing flame-retardant inorganic powder and excellent in frame retardance and compression strength. CONSTITUTION:This flame retardant paper is produced by adding a synthetic resin having methylol group in an amount of 2-10wt.% (expressed in terms of solid content) based on absolute weight of inorganic paper to inorganic paper containing 65-80wt.% flame-retardant inorganic powder based on absolute weight and then heating and drying this inorganic paper to subject the methylol group in the synthetic resin to cross-linking reaction. The resultant flame-retardant paper has excellent flame retardance of inorganic paper itself and excellent compression strength provided by cross-linking reaction of the methylol group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a flame-retardant paper as a base material for producing a paper honeycomb core,
More specifically, it relates to a method for producing a flame-retardant paper for a paper honeycomb core having excellent flame retardancy and compressive strength.

[0002]

BACKGROUND OF THE INVENTION Flame-retardant paper is widely used as a wall covering material, a building base material, a base material for electronic devices, etc., and also as a base material for making a paper honeycomb core. For such flame-retardant paper, cellulose pulp is used as a fiber, and a paper obtained by papermaking with a paper machine is coated or impregnated with a flame retardant, or as a fiber, a small amount of synthetic fiber or inorganic fiber is added to the cellulose pulp. It is known that a raw material obtained by using a papermaking machine together with a raw material prepared by adding a flame-retardant organic substance or inorganic substance to the papermaking machine is used. A typical inorganic paper produced by mixing paper with flame-retardant inorganic powder together with fibers is an inorganic paper obtained by adding aluminum hydroxide powder as an inorganic powder to pulp fiber and mixing with paper. .

[0003]

However, such an inorganic paper contains an inorganic substance which imparts flame retardancy in the form of powder, and has a large content, and the content of pulp fibers constituting the paper is small. Therefore, the strength of the paper becomes low.
When a paper honeycomb core made of such an inorganic paper is used as a building base material, there is a problem that the compression strength and the impact resistance are inferior even though the flame retardancy is excellent.

A method for improving the compressive strength of a paper honeycomb core made of inorganic paper is disclosed in, for example, Japanese Patent Laid-Open No. 5-5.
In Japanese Patent No. 7825, it is proposed to impregnate a paper honeycomb core made of inorganic paper with water glass.
However, although this method improves the compressive strength, it requires an additional step of impregnating with water glass, which inevitably increases the manufacturing cost.

Therefore, an object of the present invention is to provide a method for producing a flame-retardant paper for a paper honeycomb core, which is made of an inorganic paper containing a flame-retardant inorganic powder and is excellent in flame retardancy and compressive strength. is there.

[0006]

That is, a method for producing a flame-retardant paper for a paper honeycomb core according to the present invention comprises a fiber and a flame-retardant inorganic powder as a main component, and the flame-retardant inorganic powder is removed. After adding the synthetic resin having a methylol group to the inorganic paper containing 65 to 80% by weight based on the dry weight of 2 to 10% by weight based on the dry weight of the inorganic paper based on the solid content,
This inorganic paper is heated and dried to cross-link the methylol groups in the synthetic resin.

According to the above-described present invention, the methylol group in the synthetic resin contained in the inorganic paper is dehydrated and condensed during heating and drying to cause a cross-linking reaction. It is possible to manufacture a flame-retardant paper that has excellent compression strength in addition to flame retardancy. When a paper honeycomb core is produced using the flame-retardant paper manufactured in this way, a paper honeycomb core excellent in flame retardancy and compressive strength can be obtained.

Fibers used in the inorganic paper in the present invention include bleached softwood kraft pulp (NBKP), bleached hardwood kraft pulp (LBKP), bleached softwood sulphite pulp (NBSP), bleached sulphite hardwood (LBSP) and thermo. There are mechanical pulp (TMP), other wood pulp, etc., and one kind or two or more kinds can be appropriately selected and used from these. In addition to the wood pulp, synthetic fibers such as polyester and nylon may be used together in an amount of less than 10% by weight based on the total weight of the fibers, whereby the dimensional stability of the inorganic paper can be improved.
Further, if necessary, 5 to 15% by weight of the total fiber weight may be used in combination with inorganic fibers such as glass fiber and rock wool.
This can improve the compressive strength of the inorganic paper.

As the flame-retardant inorganic powder used for papermaking of inorganic paper, aluminum hydroxide, magnesium hydroxide, etc. can be preferably used. Since these inorganic powders undergo endothermic decomposition when heated and release water of crystallization, they have self-extinguishing properties, and as a result, they can be used as particularly excellent flame-retardant inorganic powders.

Such a flame-retardant inorganic powder is added to the fiber at the stage of paper making in the range of 65 to 80% by weight based on the absolute dry weight,
The inorganic paper can be produced by a known method, for example, using a cylinder paper machine, a Fourdrinier paper machine, a cylinder / Fourdrinier combination machine paper machine, an inclined wire paper machine and the like. If it is attempted to contain the inorganic powder in an amount of more than 80% by weight, the yield becomes poor during papermaking. Even if it is possible to contain a large amount of inorganic powder of more than 80% by weight,
Although such inorganic paper is excellent in flame retardancy,
It is inferior in terms of compressive strength. That is, JIS-
It has been found that if the compressive strength by P-8126 is 15 kgf or more, there is practically no problem as a flame-retardant paper for paper honeycomb cores. , The compressive strength is so low that this criterion cannot be reached. On the other hand, when the content of the inorganic powder is less than 60% by weight, the resulting inorganic paper has a good compressive strength but is inferior in flame retardancy and cannot be applied as a flame retardant paper for a paper honeycomb core.

The paper weight of the inorganic paper to be made is 200 to 24
It is preferably 0 g / m ² . Rice basis weight is 200g /
If it is less than m ² , the compressive strength will be relatively lowered when the honeycomb core is prepared, and if it exceeds 240 g / m ² , the manufacturing cost will be increased, which is disadvantageous.

Examples of the synthetic resin having a methylol group used in the present invention include a methylol compound of vinyl chloride / ethylene / vinyl acetate copolymer and a methylol compound of polyacrylamide, as well as a melamine resin, a urea resin, a phenol resin and an amino resin. Examples thereof include methylol compounds such as phenol resin. Of these, one kind or two or more kinds of synthetic resins are appropriately selected and used in consideration of the softening point of the synthetic resin and the like. For example, if the methylol compound of vinyl chloride / ethylene / vinyl acetate copolymer is contained alone in the inorganic paper, the synthetic resin may have a relatively low softening point and adhere to the after-dryer in the papermaking process to stain the cylinder. . In such a case, adhesion to the cylinder can be prevented by using a synthetic resin having a relatively high softening point such as a methylol compound such as melamine resin or phenol resin.

The content of the synthetic resin having a methylol group in the inorganic paper is in the range of 2 to 10% by weight based on the solid weight of the synthetic resin and the absolute dry weight of the inorganic paper. If the content is less than 2% by weight, the compressive strength of the inorganic paper cannot reach the desired level. On the other hand, if the content exceeds 10% by weight, the compressive strength will increase to some extent, but the amount of combustibles in the inorganic paper will increase, and the calorific value during combustion will increase, which is not suitable.

As a method of incorporating a synthetic resin having a methylol group into an inorganic paper, a predetermined amount of the synthetic resin may be added in the process of making the inorganic paper, or the synthetic resin may be added after the inorganic paper is made. Good. Specifically, it can be contained in the inorganic paper by using a known size press coater, roll coater, blade coater, bar coater, air knife coater or the like on machine or off machine. Alternatively, the inorganic paper may be impregnated with a bath containing a synthetic resin solution and then squeezed with a squeezing machine to adjust the content to a predetermined value.

The inorganic paper containing the synthetic resin having a methylol group as described above is then dried by heating with a dryer to dehydrate and condense the methylol group in the synthetic resin to cause a cross-linking reaction. Burnable paper can be produced. By this heat drying, the water content of the inorganic paper is usually adjusted to 4% by weight or less. When a methylol compound of various synthetic resins as described above is used, it is generally heated and dried in the range of 90 to 240 ° C. If the heating temperature is lower than 90 ° C, the crosslinking reaction of the methylol group may not be completed sufficiently. Further, if the heating temperature is higher than 240 ° C., the inorganic powder in the inorganic paper releases water of crystallization and undergoes endothermic decomposition, which may result in loss of flame retardancy of the inorganic paper, which is not preferable. While heating and drying, the methylol group undergoes a cross-linking reaction, which significantly improves the compressive strength of the inorganic paper.The paper honeycomb core made of this inorganic paper has excellent flame retardancy and compressive strength. Can be given.

[0016]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. All% in the examples and comparative examples represent% by weight.

Examples 1 and 2 Paper was made on a Fourdrinier paper machine using aluminum hydroxide as the inorganic powder and bleached softwood kraft pulp as the fiber. The aluminum hydroxide content was 78% and the rice basis weight was 220 g / m ^2.
Papermaking of the inorganic paper of. This inorganic paper is 297mm × 2
It was cut into a sheet having a size of 10 mm and used for the following experiment.

As the synthetic resin having a methylol group, a methylol compound of vinyl chloride / ethylene / vinyl acetate copolymer (trade name "Sumikaflex S830", manufactured by Sumitomo Chemical Co., Ltd.) 66%, a polyacrylamide methylol compound (trade name " Santax SP67 ", manufactured by Mitsui Toatsu) 17
%, 17% of a melamine resin methylol compound (trade name “Euramine P6300”, manufactured by Mitsui Toatsu) was prepared as a synthetic resin mixed aqueous solution (solid content concentration 20%).

After impregnating the thus obtained inorganic paper with this synthetic resin mixed aqueous solution, the content is adjusted with a roll type squeezing machine, and the solid content is 2.4% based on the absolute dry weight of the inorganic paper.
An inorganic paper with a synthetic resin content of (Example 1) and 9.6% (Example 2) was produced. These inorganic papers were heated and dried for 20 seconds in a drum dryer having a mirror-finished surface at 120 ° C. to produce flame-retardant papers with a water content of 3%.

The compression strength of the flame-retardant paper thus obtained was measured according to the method for testing the compression strength of paperboard (ring crush method) described in JIS-P-8126. Furthermore, a 25 mm cell paper honeycomb core made using these flame-retardant papers was subjected to a base material test by the method described in Ministry of Construction Notification No. 1828, and the heat generation temperature during combustion was 5
The pass / fail was judged as 0 ° C or less being passed, and higher than 50 ° C being rejected. The results are shown in Table 1.

Examples 3 and 4 In the same manner as in Example 1, except that inorganic paper containing 68% of aluminum hydroxide was used as the inorganic powder.
2.4% by weight of synthetic resin based on absolute dry weight of inorganic paper
An inorganic paper containing (Example 3) and 9.6% (Example 4) was produced, and this was heated and dried to produce a flame-retardant paper.
Table 1 shows the results of measuring the compressive strength of these flame-retardant papers and further conducting a substrate test on the paper honeycomb cores made from these flame-retardant papers.

Comparative Examples 1 and 2 By the same method as in Example 1 except that inorganic paper containing 82% of aluminum hydroxide was used as the inorganic powder.
2.4% by weight of synthetic resin based on absolute dry weight of inorganic paper
Inorganic paper containing (Comparative Example 1) and 9.6% (Comparative Example 2) was produced and dried by heating to produce flame-retardant paper.
Table 1 shows the results of measuring the compressive strength of these flame-retardant papers and further conducting a substrate test on the paper honeycomb cores made from these flame-retardant papers.

Comparative Examples 3 and 4 By the same method as in Example 1 except that inorganic paper containing 62% of aluminum hydroxide was used as the inorganic powder.
2.4% by weight of synthetic resin based on absolute dry weight of inorganic paper
An inorganic paper containing (Comparative Example 3) and 9.6% (Comparative Example 4) was produced, and this was heated and dried to produce a flame-retardant paper.
Table 1 shows the results of measuring the compressive strength of these flame-retardant papers and further conducting a substrate test on the paper honeycomb cores made from these flame-retardant papers.

Comparative Examples 5 and 6 Inorganic paper containing 78% aluminum hydroxide was used as the inorganic powder, and in the same manner as in Example 1, the synthetic resin was added in a solid content of 1.6 per absolute dry weight of the inorganic paper. % (Comparative Example 5) and 11.0% (Comparative Example 6) were produced, and this was heated and dried to produce flame-retardant paper. Table 1 shows the results of measuring the compressive strength of these flame-retardant papers and further conducting a substrate test on the paper honeycomb cores made from these flame-retardant papers.

Comparative Examples 7 and 8 In the same manner as in Example 1 except that inorganic paper containing 68% aluminum hydroxide was used as the inorganic powder.
1.6% by weight of synthetic resin based on absolute dry weight of inorganic paper
Inorganic paper containing (Comparative Example 7) and 11.0% (Comparative Example 8) was produced and dried by heating to produce flame-retardant paper. Table 1 shows the results of measuring the compressive strength of these flame-retardant papers and further conducting a substrate test on the paper honeycomb cores made from these flame-retardant papers.

[0026]

[Table 1] Inorganic powder Synthetic resin Flame-retardant paper Physical properties Content (%) Content (%) Compressive strength (kgf) Substrate test Example 1 78 2.4 16 Pass Example 2 78 9.6 34 Pass Example 3 68 2.4 20 Pass Example 4 68 9.6 37 Pass Comparative Example 1 82 2.4 4 Pass Comparative Example 2 82 9.6 10 Pass Comparative Example 3 62 2.4 23 23 Fail Comparative Example 4 62 9.6 39 Fail Comparative Example 5 78 1.6 10 Pass Comparative Example 6 78 11.0 35 Fail Comparative Example 7 68 1.6 12 Pass Comparative Example 8 68 11.0 38 Fail

As can be seen from Table 1, the flame-retardant paper of the present invention has a compressive strength of 15 kgf or more and is excellent in flame retardancy (Examples 1 to 4). The compressive strength is affected by the content of the inorganic powder, and the upper limit of the content of the inorganic powder is 80%. On the other hand, the flame-retardant paper containing a large amount of inorganic powder has extremely low compressive strength and is excellent in flame retardancy, but is not suitable for practical use (Comparative Examples 1 and 2). When the content of the inorganic powder is less than 65%, the compressive strength is excellent, but the flame retardance is poor, so that it is not suitable for practical use (Comparative Examples 3 and 4).

Further, if the content of the inorganic powder is in the proper range, the flame-retardant paper is excellent in flame retardancy. However, if the content of the synthetic resin having a methylol group is low, the compressive strength is poor and it is suitable for practical use. None (Comparative Examples 5 and 7). On the other hand, if the content of the synthetic resin is too high, the compressive strength will be rather excellent, but the flame retardance will be poor, which is not practical (Comparative Examples 6 and 8).

[0029]

As described above, the flame-retardant paper according to the present invention comprises a flame-retardant inorganic paper containing a synthetic resin having a methylol group, which is heat-dried to cross-link the methylol group. Therefore, it has high compressive strength. As a result, the paper honeycomb core made from this flame-retardant paper has excellent flame retardancy and compressive strength, and is particularly widely used as a paper honeycomb core for building base materials that require these physical properties. be able to.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location D21H 27/00 7199-3B D21H 5/00 E (72) Inventor Yasuyuki Yamachi 8-10 Shimorenjaku, Mitaka City, Tokyo No. 16 Nittetsu Mining Co., Ltd. (72) Inventor Satoshi Nakamura No. 16-16 Shimorenjaku, Mitaka City, Tokyo Metropolitan Government Nittetsu Mining Co., Ltd.

Claims (1)

[Claims] 1. A paper made mainly of fibers and a flame-retardant inorganic powder, and the flame-retardant inorganic powder being 65 to 8 per absolute dry weight.
Into the inorganic paper containing 0% by weight, a synthetic resin having a methylol group is added in a solid content of 2 to 1 per absolute dry weight of the inorganic paper.
A method for producing a flame-retardant paper for a paper honeycomb core, characterized in that after containing 0% by weight, the inorganic paper is dried by heating to crosslink the methylol groups in the synthetic resin.