JP2591672B2 - Method for producing sheet-like molded cellulose sponge - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to the production of a sheet-shaped molded cellulose sponge obtained by molding a mixture of viscose with reinforcing fibers and crystal glauberium into a sheet, coagulating and regenerating. It is about the method.

(Prior art and its problems) In order to produce a cellulose sponge, a viscose is mixed with a reinforcing fiber and crystal mirabilite, and the resulting viscose mixture is molded, heated and coagulated, and then subjected to an acid treatment to perform the bismuth treatment. Methods for regenerating the course to cellulose are known. The cellulose sponge thus obtained has a very high hydrophilicity because cellulose is used as a matrix of the sponge, and is widely used as a cleaning tool for automobiles, dishes, etc. by utilizing its properties.

By the way, in order to produce a sheet-like sponge, generally, a reinforcing fiber and crystal mirabilite are added to viscose and mixed, and after filling this mixture in a molding can, the mixture is heated and solidified, regenerated, and the obtained block-shaped sponge is obtained. A method of cutting a sponge into a sheet has been used. However, in this method, since a block-shaped sponge is once produced and then cut into a sheet, there is a problem that the productivity of the sheet-like sponge production method is poor.

On the other hand, in order to obtain a sheet-like sponge, there is also known a method in which a mixture of viscose, reinforcing fiber, and crystalline sodium sulfate is formed into a sheet, which is heated and solidified, and regenerated (Japanese Patent Publication No. 39-26285, Japanese Patent Publication No. 42-15787). This method
Since the sponge in the form of a sheet or cloth can be continuously produced, the sponge is excellent in productivity as compared with the above-mentioned method. In addition, since the sponge is inexpensive, the use thereof is expanding, especially for sanitary materials.

However, the sheet-like sponge thus obtained (hereinafter referred to as a sheet-like molded sponge) is
Compared with the sheet sponge obtained by cutting the block sponge, the liquid sponge is inferior in liquid absorbing ability and wet recovery property, and its performance is still insufficient for use as an absorbent sheet for liquid absorbent articles such as sanitary napkins. There was a problem that it was enough.

(Problems of the Invention) It is an object of the present invention to provide a method for producing a sheet-shaped molded cellulose sponge having improved liquid absorbing ability and wet recoverability.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have used a regenerated cellulose fiber having a fineness of 1 to 12 denier as a reinforcing fiber and a sheet of a viscose mixture. The present inventors have found that the problem can be solved by previously swelling the regenerated cellulose fiber with viscose and allowing the viscose to penetrate into the fiber when molding into a shape, and have completed the present invention.

According to the present invention, a regenerated cellulose fiber having a fineness of 1 to 12 deniers is added as a reinforcing fiber to viscose having an alkali concentration of 3 to 10% by weight, and mixed over 10 minutes or more. After swelling and infiltrating the viscose into the regenerated cellulose fibers, crystal mirabilite is added and mixed, the resulting mixture is formed into a sheet having a thickness of 30 mm or less, coagulated, and regenerated. A method for producing a sheet-shaped molded cellulose sponge is provided.

The reinforcing fibers used in the present invention are composed of regenerated cellulose fibers (hereinafter, also simply referred to as cellulose fibers). Various conventionally known cellulose fibers are used. As such, for example, regular type, strong type, high wet modulus type, polynosic type, high elongation type, high crimp type, flat type,
There are hollow types and the like, and staples and filaments may be used. Preferably, a regular type is used in view of the cross-sectional shape of the fiber and the water absorption / swelling characteristics. It is important that the fineness of the cellulose fiber used in the present invention is specified to be 1 to 12 denier. When the fineness of the cellulose fiber is smaller than 1 denier, in the production of a cellulose sponge, it is easy to progress from swelling to gelation during mixing with viscose, and the fiber is deteriorated in a heat coagulation step after sheet molding,
The reinforcing effect is lost, and the liquid absorbing ability and the wet recoverability are impaired. On the other hand, when the fineness is larger than 12 denier, the elasticity and the wet recovery of the obtained sponge are impaired. The preferred fineness of the cellulose fibers is 3 to 8 denier. The length of the cellulose fiber is not particularly limited, but the dispersibility of the fiber,
Since it affects the strength of the sponge, the fiber orientation when forming into a sheet, and the like, it may be appropriately selected in consideration of the use of the sponge. Generally, the length of the cellulose fiber is 5
It is better to be within the range of ~ 15mm. Further, in the present invention, the cellulose fiber, if necessary, other reinforcing fibers within a range that does not inhibit the object of the present invention, for example, natural fibers such as ramie, cotton, pulp, and synthetic polyesters, polyamides, and the like. Fibers may be added.

In the method for producing a sheet-like molded cellulose sponge of the present invention, a regenerated cellulose fiber having a fineness of 1 to 12 denier is added as a reinforcing fiber to a viscose having an alkali concentration of 3 to 10% by weight, and it takes 10 minutes or more. After mixing and swelling the regenerated cellulose fiber and allowing the viscose to penetrate into the regenerated cellulose fiber, the crystal-blended nitrate was added and mixed, and the resulting mixture was formed into a sheet, which was heat-coagulated. Thereafter, the cellulose is regenerated by contact with an acidic aqueous solution, and then washed with water and dried.

The concentration of cellulose in the raw material viscose is not particularly limited, but is usually preferably set to 8 to 10% by weight. The definition of the alkali concentration in the viscose is important, and in the present invention, it is preferably set to 3 to 10% by weight. If the alkali concentration is less than 3% by weight, the dissolution of cellulose xanthate becomes insufficient, the swelling of the cellulose fiber becomes insufficient, and the viscose does not penetrate into the cellulose fiber. On the other hand, when the alkali concentration is higher than 10% by weight, the cellulose fibers begin to gel after swelling, and the coagulation rate is slowed down in the subsequent heating and coagulation step, and the reinforcing effect due to the deterioration of the cellulose fibers is reduced. Lost. The viscosity of the raw material viscose is not particularly limited, but is preferably set to 20 to 100 poise. At viscosities below 20 poise, the resulting sheet shaped sponge is:
Its strength is low, and when wet, it is flexible, but tends to dry and brittle. On the other hand, if the viscosity is higher than 100 poise, the mixing and dispersibility of the cellulose fibers when mixing and dispersing the cellulose fibers in the viscose becomes poor, and the penetration of the viscose into the inside of the cellulose also becomes poor. It becomes hard.

The amount of cellulose fiber added to viscose is generally
The proportion is such that its proportion in the sponge is between 20 and 50% by weight. That is, it is 20 to 50% by weight based on the total amount of cellulose and cellulose fibers in the viscose. When the amount is less than 20% by weight, the obtained sponge has a large shrinkage upon drying, and lacks the elasticity and flexibility of the sponge. On the other hand, if the amount is more than 50% by weight, the liquid absorbing ability and the wet recoverability are reduced. Therefore, in the present invention, it is preferable that the addition amount of the cellulose fiber is specified in the range of 30 to 40% by weight.

In the present invention, the cellulose fiber is added to and mixed with the viscose, and then the crystalline sodium sulfate is added and mixed. In this case, the time for mixing the viscose and the cellulose fibers is such that the cellulose fibers swell and the viscose sufficiently penetrates the fibers. In the case of the present invention, generally, 10 minutes is used.
Minutes of time are employed. If the mixing time is shorter than 10 minutes, the viscose does not sufficiently swell and penetrate the cellulose fibers, and the bonding between the cellulose fibers and the cellulose becomes insufficient. Performance is also poor.

The mixing time refers to an average contact time between the viscose and the fiber from the time when the fiber is added to and mixed with the viscose to the time when the crystalline sodium sulfate is added.

In the present invention, the crystalline sodium sulfate is added to and mixed with the mixture of cellulose fiber and viscose obtained as described above. The temperature at the time of mixing of the sodium sulfate is 5 to 15 ° C. This crystalline sodium sulfate is a means for forming a foam structure of a sponge,
Its average particle size is about 0.6-5 mm. The amount of crystal salt added is appropriately determined according to the desired density of the sponge. If the addition ratio is large, the density of the sponge is reduced, and the flexibility is improved but the strength is reduced. On the other hand, if the addition ratio is small, the density of the sponge increases and the strength increases, but the flexibility decreases. In general, the amount of crystalline sodium sulfate added is 25 to 65 times the weight of the total amount of cellulose and cellulose fibers in viscose. Since the flexibility of the sponge greatly varies depending on the particle size of the crystalline sodium sulfate, the particle size is appropriately determined according to the purpose of use of the sponge. Crystalline sodium sulfate added to viscose is used for subsequent coagulation and regeneration processes,
It is eluted and removed from the sponge in the washing step.

The formation of the mixture of viscose, cellulose fiber, and sodium sulfate in the form of a sheet can be performed by extrusion. The viscose mixture formed into a sheet is coagulated by heating in a coagulation bath. As the heating temperature, a temperature of 90 to 100 ° C. is generally adopted. In this case, in order to shorten the heat treatment time, sulfuric acid or sulfuric acid / zinc sulfate treatment may be performed before the heat treatment of the viscose mixture. The viscose mixture formed into a sheet and coagulated by heating is subjected to acid regeneration and neutralization, then washed with water, dehydrated and dried by a conventional method to obtain a sheet-like sponge. The thickness of the molded sponge produced by the present invention is 30 mm or less, preferably 0.1 mm.
5 to 10 mm. This sheet-shaped sponge is made into a product as it is or by compression. In addition, a thick sheet-shaped sponge can be cut into a thin sheet and made into a product as it is or by compression.

When manufacturing the viscose sponge of the present invention, other auxiliary components such as a coloring agent, a deodorant, an antibacterial agent, and a bactericide can be added to the viscose as needed.

In the present invention, various surfactants can be added as a dispersant in order to promote dispersion of the cellulose fibers and penetration of the viscose into the cellulose fibers. Also,
A polyol compound, a chemically modified cellulose, urea, or the like can be added as an improver for improving the performance and flexibility of the sheet-like molded sponge. The amount of the surfactant used as a dispersant is preferably in the range of 0.1 to 2% by weight based on the viscose. The amount of the modifier such as a polyol compound to be added is preferably in the range of 1 to 10% by weight based on the viscose.

Examples of the surfactant include water-soluble anionic surfactants such as sodium α-olefin sulfonate having 14 carbon atoms, sodium lauryl sulfate, and sodium polyoxyethylene lauryl ether sulfate (3 moles of ethylene oxide added). , Tween 80, carbon number 1
HLB1 such as diethanolamide, polyoxyethylene lauryl ether (ethylene oxide addition mole number 8)
Zero or more nonionic surfactants are included.

Examples of the polyol compound include, in addition to glycerin, polyalkylene glycols such as polyethylene glycol and polypropylene glycol. The average molecular weight of the polyol compound is in the range of 90 to 10,000, preferably 600 to 6,000.

(Effect of the Invention) The regenerated cellulose fiber has low crystallinity compared to other fibers (about 35% in a regular type), and, combined with being formed from cellulose, absorbs water and easily swells. . For example, the swelling ratio of regular type cellulose fibers reaches 45-55% in fiber diameter and 110-130% in volume. In the present invention, by using such a cellulose fiber as a reinforcing fiber, it is a sheet-like molded product having a thickness of 30 mm or less, as well as a sponge obtained by cutting a conventional pre-formed block-shaped molded sponge into a sheet shape. The present invention has succeeded in developing a method for producing a sheet-shaped molded cellulose sponge having high liquid absorbing ability and wet recoverability, excellent flexibility, and excellent strength.

As the reinforcing fiber, conventionally, natural fibers such as hemp, cotton, and pulp, and synthetic fibers such as polyester are used.
Since these materials are inferior in swelling in viscose, even if a sheet-like molded sponge is manufactured using these as reinforcing fibers, a product excellent in liquid absorbing ability, wet recovery property and flexibility can be obtained. Can not. That is, such fibers are mixed with viscose together with crystalline sodium sulfate, the viscose mixture is formed into a sheet, and a coagulating liquid (boiling water) is formed.
When the treatment is carried out, the reinforcing fibers do not show swelling properties, and a mixture of viscose and reinforcing fibers cannot be obtained. The phenomenon occurs such that the viscose solidifies after the crystal mirabilite has flowed out of speed. As a result, the obtained sheet-shaped molded sponge has an insufficient cell structure, a high density, and is inferior in liquid absorbing ability, wet recovery property and flexibility.

On the other hand, in the case of the present invention, by using the cellulose fibers having excellent swellability as described above as the reinforcing fibers, it is possible to obtain a product in which the above-mentioned disadvantages found in the conventional sheet-like molded sponge are overcome. Can be. That is, when the cellulose fiber is added and mixed in the viscose, the cellulose fiber is sufficiently swollen without causing gelation in the viscose, and the viscose can be penetrated into the cellulose fiber. A mixture in which the used cellulose fibers and viscose are integrated can be obtained. And when adding and mixing crystal sodium sulfate to such a viscose mixture, and forming into a sheet, early outflow of the crystal sodium sulfate in the coagulation liquid is prevented, the cell structure is sufficiently developed, and the cellulose fiber is formed. Reinforcing fibers,
A sheet-shaped molded sponge in which regenerated cellulose forming a sponge matrix is integrally bonded can be obtained.

The sheet-like molded cellulose sponge obtained by the method of the present invention generally has a liquid absorption capacity of 7 (g / g) or more and a wet recovery rate of 70% or more. Such a high liquid absorption capacity and wet recovery rate cannot be easily achieved by a conventional sheet-like sponge. Further, the sheet-like molded sponge of the present invention has excellent mechanical strength (rupture strength) while having a low density. In addition, the sheet-like molded sponge of the present invention can be manufactured continuously and inexpensively using an extruder.

The sheet-shaped molded sponge of the present invention can be advantageously used as a liquid absorbent for sanitary napkins and disposable diapers, a dewatering sheet, and the like.

(Example) Next, the present invention will be described in more detail with reference to examples.

In addition, all the parts and% shown below are based on weight. In addition, the liquid absorption ability, wetness recovery rate and flexibility were measured as follows.

(1) Absorbency (AT) Two sponge sheet samples are stacked, sandwiched between the upper and lower wire meshes, and a load of 50 g / cm ² is applied on the sponge sheet sample.
Immerse in a 5 ° C. water bath for 5 minutes. Next, under this load, after lifting from the water bath and draining for 3 minutes, the weight of the water-absorbing sponge is measured, and the liquid-absorbing ability is calculated by the following equation.

AT: Absorption capacity g: Weight of sponge before absorption g ': Weight of sponge after absorption (2) Wet recovery rate (RD) It indicates whether it is easy to return to the maximum volume when wet again, and is measured as follows.

After the regeneration, the wet sponge sample containing water after washing with water is dried, immersed in a water bath at 25 ° C. for 3 minutes, the thickness is measured without load, and the thickness is calculated by the following equation.

RD: Wet recovery rate t: Thickness of wet sponge before drying t ': Thickness of wet sponge after immersing dry sponge in a water bath for 3 minutes (3) Flexibility Including water after washing and water washing after regeneration A sponge sample obtained by drying was subjected to a sensory test by five women and evaluated.

◎: Very good ○: Good △: Normal ×: Not good Example 1 (Preparation of viscose stock solution) LBSP was used as a pulp raw material, which was alkali-soaked, squeezed and crushed by a usual method, and then heated at 70 ° C. After aging for 3 hours, cellulose xanthate is obtained using 35% by weight of carbon disulfide, based on the weight of the pulp. This cellulose xanthate is dissolved in an aqueous solution of caustic soda to obtain viscose having a cellulose concentration of 9% and an alkali (NaOH) concentration of 6%. This viscose was aged at 20 ° C. for 15 hours to obtain a viscose stock solution.

(Preparation of Viscose Mixture) To 100 parts of the viscose stock solution, 4 parts of reinforcing fibers were added, and if necessary, 0.7 part of a dispersant (a sodium salt of an α-olefin sulfonic acid having 14 carbon atoms) and 0.7 part of a modifier (a molecular weight of about Polyethylene glycol (2 parts) was added and mixed at a mixing time of 10 minutes and a mixing temperature of 10 to 13 ° C.
50 parts were added and kneaded for 10 minutes to prepare a viscose mixture for molding.

(Production of sponge) The viscose mixture was supplied to a hopper of an extruder and continuously extruded from the die into a sheet having a thickness of 5 mm and a width of 150 mm at an extrusion speed of about 0.8 m / min. The extrudate was subjected to a 40 mesh stainless steel mesh. In this case, the extruder consists of a hopper, cylinder, die and rotor pump (rotor diameter 20 mm).
The hopper, cylinder and die were provided with a cooling jacket, and the viscose mixture was cooled through cooling water at 13 ° C.

The sheet-like extruded product thus obtained on the wire mesh was covered with a 40-mesh stainless steel wire mesh, and put into a boiling water bath to solidify. The bath ratio at this time was 10 times, and the coagulation time was 60 minutes. Then, after the acid regeneration treatment by a conventional method, neutralization, water washing and dehydration treatment, and further dried at 80 ℃ until the water content is 10% or less,
A sheet-shaped molded sponge was obtained.

After each dried sponge sheet having a thickness of 5 mm obtained as described above was compressed to a thickness of 0.5 mm with a press roll, the center portion was cut into a rectangular body having a length of 100 mm and a width of 50 mm. It was used as a test sample. Table 1 shows the results.

As can be seen from the results shown in Table 1, the sheet-shaped molded sponge of the present invention is a sheet-shaped molded sponge by using cellulose fibers as reinforcing fibers,
It turns out that it is excellent in liquid absorption ability, wet recovery rate, and flexibility. The performance is further improved by using a dispersant and a modifier together.

Example 2 In Example 1, a viscose stock solution in which the alkali concentration was variously changed (the dispersant and the improving agent were not used)
And a 5 mm thick sheet-like molded sponge was produced in the same manner except that cellulose fibers having a fineness of 5 denier and a fiber length of 10 mm were used as the reinforcing fibers. The performance of this sponge is shown in Table 2 together with the alkali concentration and viscosity (20 ° C.) of the used viscose stock solution.

Example 3 In Example 1, an alkali concentration was adjusted to 6%, and a viscose stock solution to which a dispersant (a sodium salt of α-olefin sulfonic acid having 14 carbon atoms) was added as needed, and a fineness as a reinforcing fiber was used. A 5 mm-thick sheet-like molded sponge was produced in the same manner except that cellulose dendrites having a fiber length of 5 denier and a fiber length of 10 mm were used and the mixing time of the viscose stock solution and the reinforcing fibers was changed. Table 3 shows the performance of the obtained sponge in relation to the mixing time.

Claims (1)

(57) [Claims] 1. A regenerated cellulose fiber having a weave of 1 to 12 denier is added as a reinforcing fiber to viscose having an alkali concentration of 3 to 10% by weight, and mixed over 10 minutes or more.
After swelling the regenerated cellulose fiber and infiltrating the viscose into the regenerated cellulose fiber, adding and mixing crystal mirabilite, forming the resulting mixture into a sheet having a thickness of 30 mm or less, coagulating and regenerating. A method for producing a sheet-shaped molded cellulose sponge, comprising: