JP3518120B2 - Paper laminate - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate, and more specifically, it relates to a packaging material such as a container mainly made of paper used for transportation, storage or preservation of foods, chemicals, industrial products, etc. The present invention relates to a laminate used as a material.

[0002]

2. Description of the Related Art It is common practice to impregnate a base paper with a resin, wax or the like in order to improve the paper properties such as water resistance, strength of paper and strength between layers of paper. The characteristics required for the base paper to be impregnated with are that there is no breakage or breakage of the base paper during impregnation, and that the penetration speed of the resin solution is high, in order to improve the working efficiency of the resin impregnation process, Is required to be retained in the base paper, and there is little unevenness of resin impregnation.

Therefore, bleached kraft pulp (LBKP) from domestic hardwood is generally used as the impregnated base paper as it is without being beaten. This unbeaten pulp is usually 550 to 650 ml C.I.
F. S. Freeness (Canadian Standard Freeness) is shown. The impregnating base paper is made from this raw material pulp by a known paper machine, and the density of the base paper is 0.45 to 0.55 g.
It is a low level of / cm ³ .

Among the characteristics required for the base paper, it is considered that the density of the base paper is increased and the interfiber bond is strengthened in order to improve the paper strength. However, if the density of the base paper is increased, the paper strength is improved. However, it cannot be used because the porosity decreases and the impregnation property of the resin deteriorates.

Further, it is possible to lower the density of the base paper to raise the porosity in order to improve the impregnation property, but if the density of the base paper is lowered, the interfiber bond also lowers, so that the paper strength of the base paper decreases. If such a base paper is used, problems such as paper breakage and tearing may occur in the impregnation process, and workability may be significantly impaired. Therefore, there is an allowable limit for reducing the density of the base paper, and the density of the impregnating base paper is usually 0.48.
Often used in the range of 0.52 g / cm ³ .

Another method for improving the impregnating property is to use linter pulp (cotton fiber pulp) as the impregnating base paper. Since linter pulp has a low content of fine fibers and the fiber itself is rigid, the content of large pores in the base paper for impregnation made from this pulp is high, and the impregnation property of the resin liquid is good. is there. However, if the linter pulp is used in the unbeaten state, the paper strength of the base paper is weak and there is a risk of paper breakage problems in the impregnation step. Therefore, when using linter pulp, the freeness value is usually 400 ml C.I. F. S. Be beaten to a certain degree. A laminated plate obtained by impregnating the impregnated base paper with a thermosetting resin and subjecting it to heat and pressure molding causes warping and twisting, has poor dimensional stability, and may cause a problem in the processing step of the laminated plate.

In a usual laminated board, a base paper for impregnation is impregnated with a thermosetting resin such as a phenol resin or an epoxy resin, and dried by heating to a semi-curable resin state (this state is called a prepreg). It is manufactured by laminating two or more sheets of the prepreg and thermoforming with a metal foil. However, in recent years, heat resistance and dimensional stability are also required for laminated boards using impregnated base paper, and the resin for impregnation has been subjected to a modification treatment to impart heat resistance, or has been conventionally used. Since polyester resin has been used in addition to the existing phenolic resin and epoxy resin,
The viscosity of the resin solution tends to increase, and the impregnation characteristics of the base paper are becoming more and more important.

[0008]

In order to solve these problems, various methods have been devised to improve the work efficiency in the resin impregnation step, but they satisfy all the required performances. Does not exist. First of all,
Since the wet strength of the base paper itself is low, the base paper is torn or cut during impregnation, which hinders the operation of the process. Secondly, since the resin is impregnated over the entire paper layer, the amount of heat required in the drying step after impregnation is enormous, which is a problem from the viewpoint of energy saving. Thirdly, since it is almost impossible to control the amount of the resin solution impregnated to give the paper base a function, the resin solution is wasted.

In view of the above situation, the inventors of the present invention have conducted intensive studies on a paper laminate which is a carrier in the impregnation step, and as a result, in a paper laminate obtained by combining a plurality of paper layers, at least one surface layer is sized. Low-size layer (however, the non-size layer is excluded)
Ku. ) (Hereinafter referred to as “low-size layer”) to improve impregnation property, and the laminate has a sizing degree of
It has been found that the water resistance of the laminate is remarkably improved by having at least one high-size layer (hereinafter, referred to as "high-size layer") having a depth of 20 seconds or more and 60 seconds or less ,
The present invention has been accomplished.

Therefore, the technical problem of the present invention is that the base paper is not broken or cut in the step of impregnating the base paper while conveying and moving the base paper, and the penetration speed of the resin solution into the base paper is high, so that it is determined. It is suitable for the impregnation process of aqueous solution, such that the weight of resin can be retained in the base paper and the resin has little impregnation unevenness. An object of the present invention is to provide a paper laminate that can control the amount of impregnation.

[0011]

In order to solve the above-mentioned problems, the invention according to claim 1 is a paper laminate in which a plurality of paper layers are combined, and the sizing degree is at least one surface layer. A paper laminate comprising at least one low size layer having a size degree of 1 second or more and less than 20 seconds and at least one high size layer.

The invention of claim 2 is characterized in that one surface layer of the paper laminate is a low size layer, and the other surface layer is a high size layer. Is.

Further, the invention of claim 3 is characterized in that both surface layers of the paper laminate are both low size layers, and the inner layer sandwiched between the both surface layers is a high size layer. Item 2. The paper laminate according to item 1.

[0014]

The invention of claim 4 is the same as claim 1 or 2.
Other The paper laminate 3 described, characterized by comprising an aqueous solution or aqueous solution containing organic metal compound alone or in combination of two or more is impregnated with a sol solution obtained by hydrolyzing and partially condensed dissolved in a solvent And a paper laminate.

Further, in the invention of claim 5 , the organometallic compound has at least two alkoxyl groups having 1 to 4 carbon atoms in the molecule, and further comprises Si, Ti, Al, B, Zr, W and Ta. The paper laminate according to claim 4, which contains at least one metal element selected from the group.

The invention of claim 6 is the same as claim 1 or 2.
Alternatively, the paper laminate according to item 3 is obtained by impregnating an aqueous solution of a self-crosslinking resin.

Furthermore, the invention of claim 7 is a paper laminate according to claim 6, wherein the aqueous solution of the self-crosslinking resin is characterized by mainly containing acrylic resin or a polyurethane resin.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

FIG. 1 is a sectional view showing an example of the constitution of the paper laminate of the present invention, and FIG. 2 is a sectional view showing another example of the constitution of the laminate of the present invention.

As described above, the paper laminate of the present invention is a paper laminate obtained by combining a plurality of paper layers, and at least one of the surface layers has a size degree of Steckigt size degree of 1 second or more. It is characterized in that it has at least one low-sized layer of less than 20 seconds and that the laminate has at least one high-sized layer.

It is sufficient that at least one surface layer of the paper laminate of the present invention is constituted by a low size layer, and preferably both surface layers of the paper laminate are constituted by a low size layer.

The simplest form of the paper laminate of the present invention is, as shown in FIG. 1, one surface layer being one low size layer 1 and the other surface layer being one high size layer 2. Is a paper laminated body consisting of two layers.

The low size layer and the high size layer do not have to be limited to single layers each consisting of one layer as shown in FIG. 1, but may be composed of two or more layers depending on the use of the paper laminate. It doesn't matter.

In a preferred embodiment of the paper laminate of the present invention, as shown in FIG. 2, both surface layers are low-size layers 1, 1 ', and an inner layer sandwiched between both surface layers. Is a high-size layer 2 which is a three-layered paper laminate.
The low-size layers 1 and 1 ′ and the inner high-size layer 2 constituting both surface layers of the paper laminate may each be one layer or two or more layers. The number of layers of the low-size layers 1 and 1'and the high-size layer 2 is arbitrarily determined depending on the application of the paper laminate used.

The low-size layer of the present invention means a layer having a size degree of Steckit's sizing degree of 1 second or more and less than 20 seconds, and the high-size layer means a Steckigt's sizing degree of 20 seconds or more 6
A layer having a size degree of 0 seconds or less.

The measurement of Steckigt sizing degree is based on JIS
It is performed according to the test method of P 8122.

As a raw material of the paper laminate of the present invention, unbeaten hardwood bleached kraft pulp is used in the low-size layers 1 and 1'having improved impregnating ability, and the high-performance layer having improved water resistance as an inner layer is used. In the size layer 2, it is preferable to use beaten softwood kraft pulp, which is dispersed by a disintegrator to form a pulp slurry, and the low size layers 1, 1 ′ are used.
About the Steckigt size degree is 1 second or more and less than 20 seconds,
A sizing agent or the like is preferably added so as to be 5 seconds or more and 15 seconds or less, and the sizing degree of the high-size layer 2 is 20 seconds or more and 60 seconds or less, preferably 30 seconds or more and 50 seconds or less in Steckigt sizing degree As described above, a sizing agent is added, and a multi-layer papermaking process using an ordinary wet paper machine is used for impregnating base paper,
That is, the paper laminate of the present invention was prepared.

As the above-mentioned sizing agent, a normal sizing agent such as a rosin sizing agent is used.

Further, the low-size layers 1, 1'of the present invention can control the impregnation amount of the resin solution to be impregnated by the size degree and / or the thickness thereof. Since it is possible to control the amount of the resin solution to be impregnated to give the paper laminate a function of improving the properties of paper, the resin solution can be effectively used. To change the sizing degree of the low-size layers 1, 1 ′, it can be achieved by changing the addition amount of the above-mentioned sizing agent, and for changing the thickness of the low-size layers 1, 1 ′, for example, the number of layers can be changed. Can be achieved by

The solution to be impregnated into the paper laminate of the present invention is an aqueous solution containing one or more organic metal compounds, or a sol solution obtained by dissolving the aqueous solution in a solvent to cause hydrolysis and partial condensation. Alternatively, an aqueous solution of a self-crosslinking resin or the like is preferable.

The above organometallic compound has 1 carbon atom in the molecule.
To 2 or more alkoxy groups of 4 to 4, and further Si, T
It is preferable that the organometallic compound contains at least one metal element selected from the group consisting of i, Al, B, Zr, W, and Ta.

Specific examples of the organometallic compound with which the paper laminate of the present invention is impregnated include silicon tetramethoxide, silicon tetrapropoxide, and epoxycyclopropylethyltrimethoxysilane.

As the sol solution of the organometallic compound, a solution containing one or more organometallic compounds is dissolved in an organic solvent represented by alcohol such as ethanol, and hydrochloric acid and water are added if necessary. Examples thereof include those that are hydrolyzed and partially condensed. The sol solution is impregnated and applied to the paper laminate and heat-treated to form a glassy film.

The paper laminate of the present invention includes one impregnated with a self-crosslinking resin solution.

Examples of the self-crosslinking resin solution of the present invention include a solution containing an acrylic resin and a polyurethane resin as main components.

The self-crosslinking resin solution is classified into a one-pack type and a two-pack type, and either one may be used for the self-crosslinking resin solution in the present invention. Further, the self-crosslinking resin solution includes both a solution containing a cross-linking agent and a solution containing no cross-linking agent. In this respect, either one may be used in the present invention. However, in view of workability, a one-pack type containing no crosslinking agent is preferable in the present invention.

Examples of the crosslinking agent used in the self-crosslinking resin solution include diisocyanate, diepoxy compound,
Examples thereof include methylol compounds and alkoxy compounds.

By the way, generally, as a method for providing a resin coating on the paper layer to improve the water resistance of the paper, a method of extruding and coding a thermoplastic resin on a paper base material, or applying a resin solution to the surface of the paper base material is carried out. After that, a method of curing a resin by using UV to form a resin film has been conventionally proposed.

However, these methods are inferior in workability and efficiency because it is necessary to process them using another device after paper making.

In the paper laminate of the present invention, a resin coating can be formed on the surface of the paper laminate by, for example, impregnating and applying the above-mentioned self-crosslinking resin solution online immediately after papermaking and heating the paper laminate normally. .

In the present invention, the wet tensile strength was measured as follows.

Wet Tensile Strength Measurement Method The paper strength of the paper laminate of the present invention is measured according to JIS P 81.
35 (paper and board wet tensile strength test method) in an environment of a temperature of 20 ° C. and a relative humidity of 65% for at least 24
From the time-conditioned humidity base paper, the width is 15
mm, length of 250 mm at least 1 each
It was cut into 0 sheets, immersed in distilled water at 20 ° C. for 10 minutes, then drained, and tested according to JIS P 8113 (testing method for tensile strength of paper and paperboard).

[0044]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Examples 1 to 6 In order to form a low-size layer, bleached hardwood kraft pulp (LBKP) was disintegrated, and the Steckigt sizing degree was 5 seconds, 1
Three types of pulp slurries were prepared by appropriately adding chemicals so that the size became as low as 0 seconds and 15 seconds. In order to form a high size layer, bleached softwood kraft pulp (NBK
P) was disaggregated and a pulp slurry was prepared by appropriately adding a chemical so that the Steckigt sizing degree was as high as 50 seconds. As the drug, Size Pine E (trade name) manufactured by Arakawa Chemical Co., Ltd. was used (the same applies hereinafter).

Using these pulp slurries, a papermaking process is carried out in a hand-made sheet machine so that both surface layers are one low-size layer and one inner layer is a high-size layer. Three types of paper laminates having a basis weight of 180 g / m ² and a low-size layer having a Steckigt sizing degree of 5 seconds, 10 seconds, and 15 seconds were produced.

Then, a sol solution using epoxycyclopropylethyltrimethoxysilane as an organometallic compound was impregnated and applied to three kinds of paper laminates having a Steckigt sizing degree of 5 seconds, 10 seconds and 15 seconds in the low size layer. Examples 1 and 2 and 3 respectively, and Examples 4 and 5 and 6 respectively impregnated and coated with a self-crosslinking resin solution containing an acrylic resin as a main component. Wet tension of each paper laminate. The strength was measured by the method described above.

Examples 7 to 12 In order to form a low-size layer, bleached hardwood kraft pulp (LBKP) was disintegrated, and a chemical agent was appropriately added so that the Stekihit sizing degree was 5 seconds. A pulp slurry was prepared. Further, in order to form a high-size layer, bleached softwood kraft pulp (NBKP) was disintegrated, and a chemical was appropriately added so as to obtain a high size of 50 seconds in a Steckigt sizing degree to prepare a pulp slurry.

Using these pulp slurries, a papermaking process was carried out in a handmade sheet machine so that both surface layers were one low-size layer and one inner layer was a high-size layer. . At this time, the basis weight of the low-size layer is 20, 40 for one layer.
And three types of paper laminates were made into paper so as to have a weight of 60 g / m ² .

The basis weight of this low-size layer is 2 per layer.
Three types of paper laminates of 0, 40, and 60 g / m ² were impregnated and coated with a sol solution containing epoxycyclopropylethyltrimethoxysilane as an organometallic compound, which were taken as Examples 7, 8 and 9, respectively. Those obtained by impregnating and coating a self-crosslinking resin solution containing a resin as a main component were designated as Examples 10, 11 and 12, respectively, and the wet tensile strength of each paper laminate was measured by the above-mentioned method.

Comparative Example 1 and Comparative Example 2 Hardwood bleached kraft pulp (LBK) used in the above examples.
P) was disintegrated and a pulp slurry was prepared so as to have no size.

Using this pulp slurry, a papermaking process was carried out with a handmade sheet machine to produce a base paper for impregnation having a basis weight of 180 g / m ² .

Then, the base paper was impregnated with a sol solution containing epoxycyclopropylethyltrimethoxysilane as an organometallic compound, and the base paper was impregnated with a self-crosslinking resin solution containing an acrylic resin as a main component. The coated sample was used as Comparative Example 2, and the wet tensile strength of each sample was measured by the method described above.

The wet tensile strength was measured by the above-mentioned method, using the paper laminate itself of Example 1 before impregnation as a reference example.

The measurement results of the wet tensile strength of the above Examples, Comparative Examples and Reference Examples are summarized in Table 1 below.

[0056]

[Table 1] As is clear from Table 1, the unsized papers of Comparative Examples 1 and 2 were hardly suitable for the impregnation step, and even if the impregnation step was possible, the workability and efficiency were poor.
Further, as shown in the reference example, the paper laminate of the present invention itself before impregnation showed a better wet tensile strength than that of only unsized paper, and was well suited for the impregnation step. Further, the paper laminate according to the present invention can effectively improve the impregnating property and significantly improve the wet tensile strength as compared with the conventional method, and depending on the sizing degree and / or the thickness of the low size layer. It was possible to control its wet tensile strength.

[0057]

As described in detail above, according to the paper laminate of the present invention, it is a paper laminate obtained by combining a plurality of paper layers, and at least one of the surface layers has a sizing degree of Suitable for impregnation of an aqueous solution by improving impregnation as a low size layer having a sizing degree of 1 to 20 seconds and having water resistance by having at least one high size layer. It became possible to control the impregnation amount of the resin solution to be impregnated by the sizing degree and / or the thickness of the low-size layer at the same time as the impregnation process of (1) was easily possible. Therefore, the paper laminate of the present invention enables a paper laminate having a significantly improved impregnation property with an aqueous solution and can control the impregnation amount of the aqueous solution, thereby improving workability and efficiency. It has an excellent effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a paper laminate of the present invention.

FIG. 2 is a cross-sectional view showing another configuration example of the paper laminate of the present invention.

[Explanation of symbols]

1 Low size layer 1'low size layer 2 High-sized layer

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-53-6606 (JP, A) JP-A-53-70109 (JP, A) JP-A-61-167099 (JP, A) JP-A-9- 123379 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (7)

(57) [Claims] 1. A paper laminate obtained by combining a plurality of paper layers, wherein at least one of the surface layers has a sizing degree of 1 to 20 seconds in terms of Steckigt sizing degree. (However, the non-size layer is excluded.)
In addition, the size degree is a Steckigt size degree for 20 seconds or more 60
A paper laminate having at least one high size layer that is less than or equal to a second . 2. One of the surface layers of the paper laminate is a low size layer.
(However, non-size layer is excluded.) And the other surface layer is
Sizing degree is Steckigt Sizing degree is 20 seconds or more and 60 seconds or less
2. The paper laminate according to claim 1, which is a high-size layer that is 3. Both surface layers of the paper laminate are low size layers (excluding non-size layers) , and the inner layer sandwiched between the both surface layers has a Steckigt size degree in size degree. Two
The paper laminate according to claim 1, which is a high-size layer having a length of 0 second to 60 seconds . 4. An aqueous solution containing one or more organometallic compounds in the paper laminate according to claim 1, 2 or 3, or a sol obtained by dissolving the aqueous solution in a solvent to cause hydrolysis and partial condensation. A paper laminate characterized by being impregnated with a solution. 5. The organometallic compound has 1 to 4 carbon atoms in the molecule.
Having at least two alkoxyl groups of
The paper laminate according to claim 4 , comprising at least one metal element selected from the group consisting of Ti, Al, B, Zr, W and Ta. 6. A paper laminate obtained by impregnating the paper laminate according to claim 1, 2 or 3 with an aqueous solution of a self-crosslinking resin. 7. The paper laminate according to claim 6, wherein the aqueous solution of the self-crosslinking resin contains an acrylic resin or a polyurethane resin as a main component.