JP2528819B2 - High wet strength paper and its manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a paper obtained by mixing a natural pulp fiber with a composite synthetic fiber and having excellent wet strength and dimensional stability.

(Prior Art) Paper using natural pulp fibers is inexpensive and has high strength when dried, good printability, and suitable hygroscopicity. Used for various purposes. However, at the time of wetting, the frictional force due to the hydrogen bond between fibers and entanglement of fibers with each other and the entanglement of fibers, which is the strong expression principle, decreases when water easily penetrates into the hydrophilic pulp, resulting in significantly strong strength. In addition to the decrease, there is a drawback that the dimensional stability when wet or after wet and then dried is poor. Various techniques have been conventionally used as means for compensating for these drawbacks, but they cannot be said to be sufficient as described below.

(1) Method of internally adding a wet strength enhancer during papermaking In the case of the wet papermaking method, a part of the wet strength enhancer is washed away into white water, and thus the wet strength cannot be effectively improved and the cost is high. become. Further, when it is repeatedly wetted, there is a drawback that the wet strength enhancer gradually drops off and loses its effect.

(2) Method of post-processing paper using natural or synthetic resin-based processing agent Although the wet strength and dimensional stability are sufficiently improved by using an appropriate processing agent, a processing step is required in addition to the paper-making process. However, there is a drawback that the process becomes complicated and accordingly the cost becomes high.

(3) Method of mixing thermoplastic synthetic fibers for papermaking A single thermoplastic synthetic fiber is mixed for papermaking, and the thermoplastic temperature of the thermoplastic synthetic fiber (the temperature at which the fibers can be heat-sealed to each other; In the case of a method in which a three-dimensional structure is formed in a sheet made by papermaking by heating above and fusing each other, the fused thermoplastic fiber has a fibrous structure collapsed by heating and has an initial strength. Since it does not hold, it does not exhibit sufficient strength, and when heated, the thermoplastic synthetic fiber shrinks, resulting in wrinkle-like defects in the resulting paper, or the size of the manufactured paper is indefinite. .

On the other hand, two or more kinds of thermoplastic synthetic fibers each having a different melting point are mixed to produce a paper, which is heated at a temperature between the respective melting points to melt a thermoplastic fiber having a relatively low melting point to form another thermoplastic synthetic fiber. The thermoplastic synthetic fiber having a relatively high melting point, which does not melt when it is fused with each other, maintains its initial strength because it retains its fibrous structure. Although some of the drawbacks of the above are solved, the drawbacks due to the shrinkage that occurs when the low-melting synthetic fiber is melted are not eliminated, and other thermoplastic properties in the sheet structure of the melted low-melting thermoplastic synthetic fiber Due to the limited opportunities for mutual contact with the synthetic fibers, the three-dimensional structure was poorly formed, and therefore the wet strength and dimensional stability were unsatisfactory.

Regarding the method of mixing the above-mentioned thermoplastic synthetic fibers, it is possible to improve the wet strength by increasing the mixing ratio of the thermoplastic synthetic fibers, but the cost becomes high and the paper using the pulp fiber is used. A defect that significantly inhibits the characteristics of

(Object of the present invention) The present invention solves the above-mentioned drawbacks of the prior art by mixing a natural pulp fiber with a composite synthetic fiber, and provides a high wet strength paper excellent in strength and dimensional stability when wet. That is the purpose.

(Structure of the present invention) The present invention comprises a natural pulp fiber (a), a fiber (b) made of a thermoplastic polymer, and a polymer (c) having a melting point lower than that of (b), A paper comprising (a) as a main component, (c) being present on the surface of (b), and (c) adhesively fixing the fibers, and (a) in the paper: The weight ratio of (b) + (c) is 60 to 98: 2
~ 40 high wet strength paper, and as a method for producing the same,
Composite synthetic fiber 2 to 2 which is composed of 60 to 98% by weight of natural pulp fiber and two or more kinds of polymer components having different thermoplasticity, and the polymer component having the lowest melting point occupies at least a part of the surface layer portion. 40% by weight is mixed to form a sheet containing the natural pulp fiber as a main component, and the sheet is formed between the lowest melting point and the highest melting point of the melting points of the polymer components forming the composite synthetic fiber. And the composite synthetic fibers are fused to each other and the fibrous structure of at least one polymer component forming the composite synthetic fibers is retained to form a three-dimensional structure in the sheet. It is a method for producing high-wet strong paper which is characterized in that

Various types of natural pulp are used as the natural pulp fiber effective in the present invention, and examples thereof include kraft pulp and chemical pulp, and the type thereof is not particularly limited. However, in order to give sufficient strength to the high-wet strength paper produced, it is desirable that the beating degree (CSF) is at least 700 cc and 500 cc.
On the other hand, the form of the composite synthetic fiber is not particularly limited, and for example, a joint type, a core-sheath type, and a polydisperse type (including so-called sea-island type, intervening type) are used. However, of the two or more kinds of polymer components forming the composite synthetic fiber, the polymer component having the lowest melting point needs to occupy at least a part of the surface layer portion of the composite synthetic fiber. For example, the outermost layer of the core-sheath type composite synthetic fiber must be the polymer component having the lowest melting point in the sea part of the sea-island type composite synthetic fiber. Specific examples thereof include ES-based fibers {Chitsuso Polypro Co., Ltd.}, NBF fibers {Daiwabo Co., Ltd.}, Melty {Unitika Co., Ltd.}, and composite synthetic fibers disclosed in JP-A-60-39412. is there. These fibers used in the present invention are cut into an appropriate fiber length if necessary, then sufficiently mixed, and paper-formed using a wet paper-making machine to produce a sheet. When the amount of the composite synthetic fiber added is less than 2% by weight, the purpose of addition is not achieved, and when the amount of the natural pulp fiber is less than 60% by weight, the characteristics of the natural pulp paper are impaired. In addition to natural pulp fibers and composite synthetic fibers, other types of natural fibers,
It is also possible to mix and use chemical fibers or synthetic fibers, and the effects of the present invention are not particularly hindered.

The sheet thus produced is heated by a cylinder type dryer or a hot roll to produce a high wet strength paper.
The strong paper thus obtained has the structure as described above, and as a result, the effects described above are obtained.

 Hereinafter, the present invention will be further described with reference to examples.

Example 1 Using a normal wet cylinder paper machine, beating degree (CSF) 650c
95% by weight of natural pulp of c and the melting point of the polymer component of the surface layer are 110 ° C, the melting point of the polymer component inside is considerably higher than 110 ° C, the core-sheath type composite synthetic fiber having a fineness of 4 denier and a fiber length of 10 mm. Melty, type 4080 {Unitika Co., Ltd.} 5% by weight was mixed and the wet sheet made into paper was dried with a Yankee type dryer having a surface temperature of 110 ° C.
100 g / m ² basis weight by heating with a multi-cylinder type heat roll with a surface temperature of 150 ℃
To obtain a high wet strength paper.

Example 2 80% by weight of the natural pulp shown in Example 1 and the melting point of the polymer component in the sea part were 105 ° C., and the fineness shown in JP-A-60-39412 was used in which an ordinary polyester polymer was used in the island part. 20 wt% sea-island composite synthetic fiber with 5 denier and fiber length of 15 mm
And were mixed by the method described in Example 1 to obtain a high-wet strong paper having a basis weight of 50 g / m ² .

Example 3 60% by weight of the natural pulp shown in Example 1 and a melting point of 100 to 110
ES fiber (EA chop) having a fineness of 3 denier and a fiber length of 5 mm, in which the melting point of one of the polymers is 165 ° C to 170 ° C.
{Chitsuso Co., Ltd.} 40% by weight was mixed to obtain a highly wet strong paper having a basis weight of 30 g / m ^{2 by} the method of Example 1.

Comparative Examples 1-2 In Example 3, the drying temperature of the wet sheet was 100 ° C.
Paper having a basis weight of 50 g / m ² was obtained by setting the heat roll temperatures to 90 ° C. and 180 ° C.

Comparative Example 3 Using the natural pulp used in Examples 1 to 3, pulp paper was obtained by the method of Example 1.

As described above, the performance of the papers obtained in Examples 1 to 3 and Comparative Examples 1 to 3 is as shown in the following table, and the high wet strength paper according to the present invention is excellent in wet strength and dimensional stability. The appearance quality was also good.

(Effects of the Invention) The high-wet strength paper according to the present invention described above has high wet strength and good dimensional stability, and at the same time, has favorable properties of pulp paper, that is, good printability and moderate hygroscopicity. keeping. When such a high-wet strength paper of the present invention is used as, for example, cardboard surface paper and wrapping paper, it is difficult to tear even when wet with rainwater or the like, and deterioration in appearance quality due to deformation is eliminated. In addition, it is used for coffee filters, sanitary materials such as disposable diapers, outdoor posting materials, confectionery wrapping paper, papers and tapes such as adhesive tapes, insulating papers, pacing materials such as napkins, taobag papers and hairdressing materials.

Claims (2)

(57) [Claims] 1. A natural pulp fiber (a), a fiber (b) made of a thermoplastic polymer, and a polymer (c) having a thermoplastic temperature lower than the thermoplastic temperature of the (b), A paper obtained by drying a wet-processed wet sheet, wherein (c) is present on the surface of (b), and (c)
Is a high-wet strong paper in which the fibers are adhesively fixed and the weight ratio of (a) :( b) + (c) in the paper is 60-98: 2-40. 2. A polymer component comprising 60 to 98% by weight of natural pulp fibers and two or more polymer components having different thermoplasticity, and having the lowest thermoplasticization temperature occupies at least a part of the surface layer portion. The formed composite synthetic fibers are mixed in an amount of 2 to 40% by weight, a sheet containing the natural pulp fiber as a main component is wet-processed, and the sheet is thermoplasticized at each of the polymer components forming the composite synthetic fiber. Among them, heating at a temperature between the lowest and highest thermoplastic temperature,
The composite synthetic fibers are alternately fused and the fibrous structure of at least one polymer component forming the composite synthetic fibers is held to form a three-dimensional structure in the sheet. Wet strength paper manufacturing method.