JPH0364598A - Laminated water-resistant paper and its production - Google Patents

Abstract

PURPOSE:To obtain the the paper excellent in writability, etc., by extruding an inorganic filler-contg. specific thermoplastic resin and an inorganic filler-free thermoplastic resin in a twolayer filmy form through a T-die under specified conditions followed by lamination on the surface of a paper substrate. CONSTITUTION:Firstly, a thermoplastic resin containing a maleic acid (derivative) graft-modified polyolefin or its blend with a polyolefin is melted and the resulting melt is incorporated with 20-80wt.% of inorganic filler comprising calcium carbonate and titanium dioxide to prepare an inorganic filler-contg. thermoplastic resin. Thence, this resin and an inorganic fillerfree thermoplastic resin are extruded in a two-layer filmy form through a T-die while muthally laminating both the resins so that, within said T-die, the latter resin is located so as to come into contact with the surface of a paper substrate, followed by lamination on the surface of said paper substrate layer, thus obtaining the objective paper excellent in printability, antistatic nature, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a laminated waterproof layer with excellent water resistance, writability, printability, low static charge, weather resistance, tear strength, dimensional stability, adhesion, and opacity. Regarding paper.

[Conventional technology]

A two-layer structure in which a paper sheet is used as a base layer and the surface thereof is coated with polyethylene containing an inorganic pigment such as titanium dioxide, zinc oxide, or zinc sulfide, or an inorganic pigment-free polyethylene layer is interposed between both layers. A support for photographic paper having a three-layer structure is known. (Tokuko Showa 49-3044
Publication No. 6) In these laminated papers, the resin layer is made opaque by the inorganic pigment, and practicality has been sufficiently imparted. However, for more advanced requirements, it is preferable to use three or more layers with an inorganic pigment-free resin layer interposed between the two layers.

This three-layer laminated paper makes the resin layer opaque by containing inorganic pigments, and also contains pigments to prevent the decrease in adhesive strength between the surface of the paper base layer and the resin layer that occurs due to the inorganic pigments (3) (4). A non-compatible resin layer is interposed. Further, it is known that a sheet formed by coextruding a composition of polypropylene and maleic anhydride graft-modified polypropylene with polypropylene has insufficient printability and antistatic properties. (Japanese Patent Publication No. 64-987) [Problems to be Solved by the Invention] In the above-mentioned support for photographic paper, polyethylene is added to the surface of the paper in order to smooth the surface of the photographic paper for printing fine photographic images. Although the resin layer was ff1M, as a result of providing the resin layer, the surface of the support became transparent.

Therefore, a pigment is included in the resin layer to form a white background so that a clear photographic image can be obtained. In other words, in photographic supports, it is desirable to incorporate inorganic pigments into the polyethylene resin layer on the surface;
On the other hand, the blending of inorganic pigments must not impair the smoothness of the surface of the resin layer. Due to this relationship, the amount of compounding is restricted, and practically 7% by weight.
It is said that there is a limit to the degree.

In contrast, the laminated waterproof paper according to the present invention has excellent printability and
Must be writable.

For this purpose, the surface of the laminated waterproof paper needs to have an appropriate level of roughness, so if the amount of inorganic pigments used in photographic supports is about 7% by weight, the surface roughness is insufficient, and water-based or It interferes with the fixing and drying of oil-based printing inks or water-based writing inks. Furthermore, even if one attempts to write with a ballpoint pen or pencil, the problem arises that it is virtually impossible to write on it, just as with the smooth film itself.

For this reason, the applicant of the present application not only provided a means to solve the above-mentioned problems in the prior art, but also incorporated a large amount of titanium dioxide or zinc oxide, which is used for opacification in photographic paper supports, into the resin layer. However, there are disadvantages arising from the inability to reduce the high chargeability of the resin layer, that is, when continuous automatic printing or electrostatic automatic copying is performed using a large number of sheets that retain such high chargeability, Mutual attraction between sheets due to static electricity (5) (6) We have provided a means to solve the problem of feeding two or more sheets in a stacked state using force, which causes troubles such as paper jams. (Patent Application No. 63-18734) However, in printing paper for book covers and packaging, it is often required that the ink does not peel off due to friction or scratching on the ink printed area after printing, but this is still not the case. No suitable method for improving this point has been found.

[Means to solve problems]

The present inventors have developed a laminated waterproof paper that has printability, writability, and adhesiveness different from existing photographic paper supports, and as a result, the outermost resin layer corresponding to the printing surface or writing surface using a graft-modified polyolefin, and further adding 20
It has been found that it is beneficial to include ~80% by weight of inorganic filler, preferably 30-50% by weight.

The graft-modified polyolefin used in the present invention is a polyolefin such as polyethylene or polypropylene that has been partially or completely graft-modified, but the monomer to be grafted (hereinafter referred to as the graft monomer) contains maleic acid or It is a derivative thereof. Derivatives include acid anhydrides, esters, amides, imides, metal salts, etc.
For example, maleic anhydride, maleic acid monoethyl ester, maleic acid diethyl ester, maleic acid monoamide, maleic acid diamide, maleic acid-N-monoethylamide, maleic acid-N,N-diethylamide, maleic acid-N-monobutylamide. , maleic acid-N, N-dibutylamide, maleimide, N-butylmaleimide, N-
Phenylmaleimide, etc. can be mentioned. Among these, maleic anhydride is most preferred.

The amount of graft monomer of polyolefin l\ (hereinafter referred to as graft ratio) is 10-4 to 3
It is preferable to adjust the amount within a range of % by weight. The crystalline polyolefin may be partially or completely grafted, but from the viewpoint of industrial production, a modified polyolefin with a grafting ratio of 10-2 to 6% by weight is prepared in advance (7). (8) It is preferable to prepare the modified polyolefin in advance and then mix the modified polyolefin with the unmodified polyolefin because the concentration of the graft monomer in the composition can be adjusted appropriately.

The thermoplastic resin of the present invention includes polyethylene resin,
Polypropylene resins and polyester resins are preferred.

Here, polyolefin is not limited to a homopolymer of 1-olefins, but also copolymers of 1-olefins, and other monomers copolymerizable with 1-olefins, such as vinyl acetate,
A copolymer containing a small amount of ethyl acrylate, methyl methacrylate, etc. may also be used.

Of course, compositions of different polymers or copolymers are also included.

(1) Polyethylene resin has a melt flow rate [MFR (190°C)] of 3 to 20 g/10 m1n
, melt tension (=melt tension, 190°C, extruder orifice L/D = 3.8, extrusion speed 15n+m/mi
n, take-up speed 15 tn/min) 0,
A weight of 3 to 11 g is preferable.

(2> Polypropylene resin has a melt flow rate [MFR (230°C) of 15 to 50 g/10 m
1n, melt tension (230°C, L/D of extruder orifice
=3.8, extrusion speed 15+n+n/min, take-up speed 15m/+n1)0.3 to 3.3.

The average particle size of the inorganic filler used is usually 0.01 to 10 μm, preferably 0.01 to 10 μm, from the viewpoint of dispersibility in the resin layer and the writability and printability that the inorganic filler imparts to the resin layer. 1 to 5μ is about 0.

Further, attributes of the inorganic filler include specific surface area and oil absorption. For example, titanium dioxide is of rutile type, has a specific surface area of 1 to 50 m2/g, and an oil absorption of 10 to 50 m2/g.
+n I/100g, for calcium carbonate,
Average particle size 0.5-10μm, specific surface area 0.5-70m2
/ g, preferably 1-30tn2/g ()IIET
method>, oil absorption is 5 to 100+nl/100g, preferably 10 to 70ml/100g, and is preferably heavy.

Other effective inorganic fillers include talc, clay, kaolin, barium sulfate, calcium carbonate, calcium silicate, magnesium carbonate, titanium oxide, zinc oxide,
Examples include magnesium oxide, silica oxide, diatomaceous earth, magnetic iron oxide, and mixtures thereof.

Note that a small amount of organic filler such as carbon black, phenol resin, melamine resin, or urea resin may be mixed in, and fatty acid salts, tackifiers, and hydrophilized polyolefins may be added as auxiliary means to improve the dispersibility of the inorganic filler. It is also possible to add wax or the like as appropriate, or to perform surface treatment on the inorganic filler with them.

In order to form a thin film with a thickness of 20 μm or less even though the inorganic filler has a high content of 20% by weight or more in the resin layer, it is necessary to control the moisture content of the inorganic filler to 5001)I)m or less. preferable.

The method for producing the laminated paper of the present invention involves extruding a polyolefin layer containing no inorganic filler on at least one side of the paper base layer using a T-die film forming machine, and then forming a polyolefin layer containing an inorganic filler separately on the upper surface. A preferred method is to laminate and bond the three layers while extruding the graft-modified polyolefin layer (hereinafter simply referred to as an inorganic filler-containing layer) from a T-die film forming machine.

Here, the thickness of each resin layer is usually 3 to 20 μm in the inorganic filler-containing layer, preferably 5 to 10 μfn, and usually 3 to 25 μfn, preferably 5 to 10 μm in the layer in contact with the paper base material.
It is set to 20μIn.

The layer thickness of the inorganic filler-containing layer may be made thicker or thinner than the layer not containing the inorganic filler. For example, the containing layer 3μI11
The thickness of the non-containing layer can be 17 μm.

The outermost layer and the resin layer in contact with the paper must be made of the same type of material, such as a combination of low-density polyethylene resins, high-density polyethylene resins, polypropylene resins, and poly-1-butene resins. is preferred. Even when these resins consist of a composition of two or more resins,
It is preferable that the breakdown of the constituent resins of each layer and the blending ratio of both layers are the same between both layers.

As a method for manufacturing the laminated paper of the present invention, there is also a method of laminating and adhering a polyolefin layer containing an inorganic filler on at least one surface of a paper base layer while extruding it from a T-die film forming machine. Product (11) (12) The waste paper obtained by this method has interlayer adhesion strength sufficient to withstand normal use.

A more preferable manufacturing method is a method in which an inorganic filler-incompatible resin layer is interposed between the paper base layer and the inorganic filler-containing resin layer, as described below. According to this method, even if the inorganic filler layer is made thinner, it becomes easier to suppress the occurrence of film breakage and perform stable molding.

Of course, the inorganic filler-containing resin layer may be laminated and bonded directly on both sides of the paper base layer, or after laminating the inorganic filler-incompatible resin layer on both sides of the paper base layer, or simultaneously with the lamination. There is no problem even if an inorganic filler-containing resin layer is further laminated and adhered to the surface of the resin layer.

Furthermore, in order to improve the adhesion with paper, the surface of the paper base layer before extrusion coating is subjected to flame treatment, corona discharge treatment, and preheating treatment, or the surface of the paper base layer to be laminated is subjected to flame treatment, corona discharge treatment, and preheating treatment. It is preferable to perform a treatment such as ozone treatment on the surface to be treated.

As a result, low-temperature adhesion is improved, and it is possible to reduce the frequency of occurrence of eye stains from the resin and to prevent resin deterioration and tear strength reduction.

The surface roughness of waterproof paper obtained by laminating a resin layer on a paper base layer can be changed by appropriately selecting the content of inorganic filler, average particle size, and thickness of the outermost layer. However, by changing the cooling roll pattern of the laminator and finishing the surface of the product with a matte finish, pencil writing ability can be improved. If necessary, antistatic agents, ink adhesion improvers, ultraviolet absorbers, etc. may be incorporated into at least a 1° layer of resin or coated on the surface of the outermost layer.

In the present invention, by combining specific types of inorganic fillers, adhesion, writability, and printability can be imparted to the resin layer without substantially increasing electrical properties.
1 can be given.

In particular, the outermost layer contains 30 to 50% by weight of an inorganic filler, and furthermore, the inorganic filler mainly consists of calcium carbonate and titanium dioxide, and the weight ratio of both is 99 = 1 to 5.
5:45, preferably 80:20-60:
40 is most desirable. In the case of such a structure, (13) (14) the surface resistance value of the outermost layer is 1×10 10 to 9×10 15 Ω, and both the writability and printability are extremely good.

Note that the surface resistance of the laminate of the present invention is a value measured at 23° C. and phase humidity (R1() 60%).

For printing paper used for book covers and packaging, it is often required that the ink does not peel off even when the ink printing area l\ is smeared or scratched after printing.

The present invention provides a means for solving this problem by incorporating graph-modified polyolefin into the resin layer to improve chemical adhesion.

〔Example〕

Examples of the present invention and comparative examples thereof are shown below.

The following physical properties were measured for the laminated waterproof papers obtained in Examples and Comparative Examples, and the results are shown in Tables 1 and 2.

[Measurement properties] [Measurement method] 1) Thickness: JIS P-81182) Writability: A pencil test was conducted under constant pressure using a pencil with a hardness of 2B.

The judgment criteria are as follows.

◎ Can write very well.

○ I can write well.

× I can't write at all.

3) Surface resistance value Model I P-6 manufactured by Nichiden Electric Co., Ltd.
The measurement was carried out using 01°VE-30 in an atmosphere of 23°C and 60% RH.

4> Printing suitability: Roland offset lithographic printing machine (
202B) was used. The dimensions of the printing paper are 297
It is 420mm (A 3) and the paper feeding speed is 8000mm.
The atmosphere in the printing room was 20° C. x 50% RH. In addition, the ink is Dainippon Ink Chemical Industry Co., Ltd. POP-S
It was used.

5) Adhesion of ink: 24 hours after printing is finished, firmly stick a cellophane tape (made by Chiban) with a width of 24+nn+ on the ink-printed surface and peel it off vigorously.

(15) (16) If no ink is removed by the sellotape at this time ◎ Slightly No ○ If it is removed × 6) Ink drying properties: After 1 hour after printing, touch the printed surface lightly with your finger to see if the ink is removed. If it doesn't stick at all ◎ 1 If it sticks a little ○ If it sticks × (Example)) Maleic anhydride graft modified polyethylene (maleic anhydride content 3% by weight, MFR 4.5, density 0.917)
90 parts by weight and low density polyethylene (MF811g/1
0 minutes, density 0.916 g/cm3, melt tension 1.3 g) 75 wt. ) in a weight ratio of 95:
Add and mix 25% by weight at a ratio of 5 to 5. This blend was extruded through a T-die at a temperature of 290°C, and while blowing ozone-containing air onto the surface of the molten film to be adhered to the paper, the blend was extruded to a thickness of 60°C.
Both sides of a waterproof copying paper having a μI of 11 and a width of 500 + nm are laminated to obtain a laminated waterproof paper. At this time, the ozone treatment conditions were as follows: lamination speed of the molten film was 100 m/min, air gap was 130 m/min.
"nm, ozone concentration 40g/+n3, ozone flow rate 2
tn 3/h. The waterproof copying paper used in this example was made of high-quality paper with a basis weight of 48 g/+03 and size press coated with a coating liquid of 80/20 starch/polyvinyl alcohol at a coating amount of 1 to 2 g/m'. This is xerographic copy paper with a Steckicht size of 30 seconds.

The results are shown in Table 1.

(Example 2) Maleic anhydride graft modified polyethylene (maleic anhydride content 0.03% by weight, MFR 8, density 0.931
)25% by weight in a molten state, and 75% by weight of calcium carbonate and titanium oxide in a weight ratio of 60:40.
Add and mix % by weight. Separately, prepare the above-mentioned low-density polyethylene that does not contain an inorganic filler, use this resin that does not contain an inorganic filler as the lower layer in contact with the paper, and use the above-mentioned inorganic filler-containing resin (17). 18) Using a resin as the outermost layer, extrude and press-bond onto both sides of the same waterproof copying paper as in Example 1 at a temperature of 290° C. from a coextrusion T-die to obtain a laminated waterproof paper. The results are shown in Group 1.

(Example 3) Maleic anhydride graft modified polypropylene (maleic anhydride content 3.0% by weight, MFR 25, density 0.90
) 10 parts by weight and polypropylene (MFR 25g/10 min, density 0.91g/c+n3, melt tension 0.5
g) 90 parts by weight of 65% by weight of the blend is in a molten state, and calcium carbonate and titanium oxide are added to this in a weight ratio of 95% by weight.
Add and mix 35% by weight at a ratio of =5. Separately, prepare the above-mentioned polypropylene that does not contain an inorganic filler, use this resin that does not contain an inorganic filler as the lower layer in contact with the paper, and use the above inorganic filler-containing resin as the outermost layer. It is extruded and pressed onto both sides of the same waterproof copying paper as in Example 1 at a temperature of 290° C. using an extrusion T-die to obtain a laminated waterproof paper. In addition, during coextrusion, the same ozone treatment as in Example 1 is applied to the surface of the molten resin film that is the lower layer in contact with the paper and is to be adhered to the paper.

(Example 4) In Example 3, titanium oxide and silica were added in addition to carbonate, and the distribution ratio was 70:20:1.
A laminated waterproof paper was obtained in the same manner, except that high-quality paper (basis weight 70 g/m3) was used as the paper base layer.

(Example 5) Example 3 was repeated except that the ratio of lucium carbonate and titanium oxide was changed to 95=5, and the coextrusion was carried out on only one side of the waterproof copying paper instead of on both sides. and obtain laminated waterproof paper.

(Examples 6 and 7) In Example 3, the blending ratio of lucium carbonate and titanium oxide used as inorganic fillers and the film thickness were changed as shown in Table 2 to obtain laminated waterproof paper.

Claims (1)

[Claims] 1. Paper is used as a base material layer, and at least one layer of thermoplastic synthetic resin is laminated on the surface thereof, and at least the outermost layer of the resin is graft-modified with maleic acid and/or its derivatives. A laminated waterproof paper containing a polyolefin or a blend of the modified polyolefin and a polyolefin, and containing 20 to 80% by weight of an inorganic filler based on the resin, and having good printability and low chargeability. 2. Paper is used as a base layer, at least one thermoplastic synthetic resin layer containing no inorganic filler is laminated on the surface thereof, and the surface of the synthetic resin layer is further coated with maleic acid and/or its derivative graft-modified polyolefin or A laminated waterproof paper comprising at least one thermoplastic synthetic resin layer containing a blend of a modified polyolefin and a polyolefin and containing 20 to 80% by weight of an inorganic filler based on the resin. 3. At least the outermost layer of the resin contains 30 to 50% by weight of an inorganic filler, and the inorganic filler mainly consists of calcium carbonate and titanium dioxide, and the ratio of the two is 80:20 to 60 on a weight basis. 40. The laminated waterproof paper according to claim 1 or 2, characterized in that the paper has a paper weight of 40. 4. A maleic acid and/or its derivative graft-modified polyolefin or a blend of the modified polyolefin and a polyolefin has a maleic acid and/or its derivative unit content of 10^-^4 to 3% by weight. The laminated waterproof paper according to any one of claims 1 to 3. 5. The laminated waterproof paper according to any one of claims 1 to 4, wherein the maleic acid and/or its derivative graft-modified polyolefin is maleic anhydride graft-modified polyethylene or polypropylene. 6. Thermoplastic resin containing molten maleic acid and/or its derivative graft-modified polyolefin or a blend of the modified polyolefin and polyolefin containing 20 to 80% by weight of an inorganic filler and no inorganic filler. Thermoplastic resin and thermoplastic resin are laminated in a T-die so that the latter resin is located on the side that is in contact with the surface of the paper base layer, and extruded from the T-die in the form of a two-layer film to be laminated and bonded to the surface of the paper base material. A method for producing laminated waterproof paper, characterized by: 7. Using paper as a base layer, at least one polyolefin resin layer containing no inorganic filler is extruded and laminated in a molten state on the surface thereof, and then the surface of the resin layer is mainly composed of calcium carbonate and titanium oxide, and Contains 20 to 80% by weight of an inorganic filler based on the resin, with a ratio of 99:1 to 55:45 on a weight basis, maleic acid and/or
A method for producing laminated waterproof paper, which comprises extruding and laminating at least one thermoplastic resin layer containing a graft-modified polyolefin or a derivative thereof or a blend of the modified polyolefin and a polyolefin in a molten state.