DE2540069C2 - Transparent paper and process for its manufacture - Google Patents

Description

is composed.

2. Transparent paper according to claim 1, characterized in that the polymer mixture also contains unreacted polyvinyl alcohol in amounts of 23 weight percent or less.

3. Transparent paper according to claim 2, characterized in that the polymer mixture also contains a polymer of acrylonitrile in amounts of 35 percent by weight or less.

4. Transparent paper according to claim 1, characterized in that the copolymer of polyvinyl alcohol and acrylonitrile is a graft copolymer.

5. Transparent paper according to claim 1, characterized in that the average degree of polymerization the polyvinyl alcohol in the copolymer of polyvinyl alcohol and acrylonitrile in the range from 500 to 3400 lies.

6. Transparent paper according to claim 1, characterized in that the polyvinyl alcohol content of the Copolymers of polyvinyl alcohol and acrylonitrile in the range from 20 to 80 percent by weight.

7. Transparent paper according to claim 1, characterized in that the acrylonitrile content of the copolymer of acrylonitrile and styrene is in the range of 5 to 45 percent by weight.

8. Transparent paper according to claim 1, characterized in that the fiber mass is substantially from 10 to 50 parts by weight synthetic paper pulp and 90 to 50 parts by weight natural pulp consists.

9. Transparent paper according to claim 1, characterized in that the natural pulp is wood pulp is.

10. A method for producing the transparent paper according to claim!, Characterized in that it by pressing under a pressure in the range of 980 to 4900 N / cm.

11. A method for producing the transparent paper according to claim 10, characterized in that it is carried out by pressing under a pressure in the range of 1176 to 3920 N / cm.

The invention relates to improved transparent paper made from a mixture of synthetic and natural Paper stock.

So far, transparent paper made of natural cellulose, such as glassine paper, has been used in practice. This transparent paper, however, has in view of the use of highly milled natural Pulp in its manufacture has various disadvantages in practical use. One of the biggest Disadvantages are that the conventional transparent paper is very sensitive to moisture or Water and is prone to stretching, curling and curling. The conventional transparent paper is suitable therefore not for offset printing, which is moistened with water, and also not for further processing aqueous coating agents ^ The conventional transparent paper also has other disadvantages, such as the formation of bubbles when heated as a result of a relatively high equilibrium content of moisture, and high bulk density due to high hydration of the pulp. Furthermore, it is in the manufacturing process of such conventional transparent paper is required. Use pulp that is easy to grind leaves, and it requires special grinding conditions depending on the type of grinding apparatus to a to accelerate the hydration of the pulp as much as possible. Furthermore, the vigorous milling leads to a Decrease in the freeness of the paper stock, which in turn reduces the speed of papermaking is restricted.

The] P-AS 35 608/1974 describes an improved process for the production of transparent paper, in

ho the polyethylene fibers or polypropylene fibers are mixed with wood / .zcllstoff to form a paper material and the paper made therefrom is then raised to a temperature above the melting point of the fibers forming the fibers Resins are heated and subjected to pressure. These poly-rt-olefin fibers have a poor dispersibility in water and therefore difficult to obtain a paper of uniform texture obtain. Since the method further involves heating the paper under pressure to a temperature above the

b ^r> melting point which is performed the lasers forming resins, the transparency of poly involved in the paper -, \ - olefin fibers as compared to that of obtained from natural cellulose fibers to high, and as a result it is extremely difficult to find a sheet of paper of uniform transparency to obtain. The transparent paper containing ΡοΙν-Λ-olefin fiber has a poor affinity for water and can therefore

hardly use for offset printing and further processing with the help of aqueous coating media, although it has a better space retention wedge. Furthermore, this paper is prone to the transparency treatment under the influence of heat and pressure to adhere to the heat roller and build up of poly-ft-olefin fibers to form on the roller.

The invention has for its object to provide a new transparent paper available that the does not have the above-described disadvantages of the conventional transparent paper and therefor various Offers advantages that have not yet been achieved with conventional transparent paper.

Another object of the invention is to provide an improved transparent paper which consists of a mixture of synthetic paper pulp and natural cellulose, the synthetic Paper stock in turn is a mixture of a copolymer of polyvinyl alcohol and acrylonitrile and one Copolymer of acrylonitrile and styrene is. Synthetic paper stock consisting essentially of a copolymer consists of acrylonitrile and styrene, is ai; known, and the production of paper from a mixture From such a synthetic paper stock with natural cellulose is proposed in DE-PS 24 37 573 been. The value of such mixtures of synthetic and natural paper stock for the production of however, transparent paper has not yet been recognized.

The transparent paper according to the invention is produced by wetting a fiber mass in the form of a sheet in such a way that it has a moisture content in the range from 5 to 40%, and then using a press at a surface temperature of at least 130 ⁰ C presses The fiber mass consists of

a) 6 to 60 parts by weight on a dry basis of a synthetic paper stock, namely a polymer mixture the

to 5 to 40 percent by weight of a copolymer of polyvinyl alcohol and acrylonitrile, in which the Polyvinyl alcohol component is chemically bound to the acrylonitrile component and the content of polymerized polyvinyl alcohol is 20 to 80 percent by weight, and 60 to 95 percent by weight of a copolymer of acrylonitrile and styrene with a content of copolymerized acrylonitrile units of 5 to 45 percent by weight, and

b) 94 to 95 parts by weight of natural pulp on a dry basis.

The synthetic paper stock used in the context of the invention is produced from a polymer mixture, 5 to 40 percent by weight of a copolymer of polyvinyl alcohol and acrylonitrile (hereinafter abbreviated as "PVA-AN copolymer") and 60 to 95 percent by weight of a copolymer Acrylonitrile and styrene (hereinafter abbreviated as "AN-S-Copolymer").

In the PVA-AN copolymer are polyvinyl alcohol (hereinafter abbreviated to "PVA"), the hydrophilic Constituent, and acrylonitrile (hereinafter abbreviated to "AN"), which forms the hydrophobic constituent, chemically bound together, e.g. B. in the form of a graft copolymer or in the form of a block copolymer. The PVA-AN copolymer is preferably a graft copolymer.

Optionally, the polymer mixture can also contain non-encapsulated PVA in amounts of 23 percent by weight or less and / or an acrylonitrile polymer in amounts of 35 percent by weight or less, each based on the total amount of the polymer mixture * included.

The PVA-AN graft copolymer used according to the invention can be produced by heterogeneous aqueous polymerization or by homogeneous solution polymerization. The mean degree of polymerization of the PVA can be in the range from 500 to 3400 and is preferably in the range from 600 to 1800. The degree of saponification of the PVA is preferably 60% or more. The polymerization of PVA with AN to form a graft copolymer can be carried out by placing the PVA in a polymerization solvent, e.g. B. dimethyl sulfoxide, dissolves, in this solution 25 to 500 percent by weight (based on the amount of PVA) AN ψ, dissolves and then in the presence of a polymerization catalyst, such as a persulfate, at room temperature or

S ^ polymerizes at a relatively low temperature, such as 70 "C or below. The end product of this

f, f polymerization can contain a PVA-AN graft copolymer, unreacted PVA and polyacrylonitrile.

^ΪΤ During the implementation for the production of the PVA-AN copolymer, a small by-product may occur

Amount of AN polymer that is not bound to the hydrophilic component and of an unreacted hydrophilic component that is not bound to the AN. develop. The presence of these by-products ^ ₁ th in the polymer mixture but is harmless, if only the mixture of the PVA-AN copolymer and

Contains s / f AN-S copolymer in the proportions given above. It is therefore not necessary to do this

t; Remove by-products from the end product of the polymerization to make the PVA-AN graft copolymer

viji. It is only essential that the AN and the PVA are chemically bonded to one another and the copoly-

ι ^Λ merisat has the PVA content specified above, which makes it possible to finally obtain

\ ^ synthetic paper stock excellent hydrophilic properties, excellent dispersibility in

S 'water and excellent self-adhesive properties. When the AN and the PVA in the mixture

j are simply present as constituents of the mixture, it is impossible to give synthetic paper stock such an intrinsic ω

"to lend stocks.

Another polymerization method can also be used, in which the AN to an aqueous PVA solution added and then the polymerization is carried out. The PVA-AN graft copolymer obtained by this process can be isolated by reprecipitation and filtering off.

The PVA content of the graft copolymer should be in the range from 20 to 80 percent by weight, preferably e> 5 35 to 65 percent by weight. If the PVA content is less than 20 percent by weight, that will Molecular weight of the grafted polyacrylonitrile too high, which impairs the processability and the development of the hydrophilic properties of the synthetic paper stock is hindered. If on the other hand

If the PVA content exceeds 80 percent by weight, the PVA would in the transfer of fibers or des Pulp in an aqueous slurry flow into the water, causing foaming in the slurry and thus lead to the hindrance of the grinding process and paper production.

The use of a PVA with an average degree of polymerization less than 500 leads to the decrease the water resistance of the paper. On the other hand, if the average degree of polymerization of the PVA exceeds 3400, the hydrophilic properties of the fibers suffer and fibrillation is not so easy perform so that you do not get a synthetic paper stock with the desired properties

In the production of the PVA-AN copolymer, in addition to the AN, other monomeric vinyl compounds, which are copolymerizable with the AN, such as. B. vinyl acetate, methyl acrylate, Siyrol and vinyl chloride, polymerize in amounts of less than 40 mole percent.

The ΛΝ content of the AN-S copolymer should be in the range from 5 to 45 percent by weight, preferably from 15 to 40 percent by weight. If this AN content exceeds 45% by weight, the compatibility becomes of the AN-S copolymer with the PVA-AN copolymer too high, reducing the shape or properties of the emerging fibrils are affected. On the other hand, when the AN content is less than 5 percent by weight, the solubility of the AN-S copolymer in a solvent (dimethyl sulfoxide) reduced, and no spinnable concentrated solution can be produced from the copolymer, so that a uniform synthetic paper stock is not obtained.

The AN-S copolymer can by conventional methods of random copolymerization, for. B. by heterogeneous aqueous polymerization or by bulk polymerization.

The polymer mixture used to produce the synthetic paper stock according to the invention contains 5 to 40 percent by weight of PVA-AN copolymer and 60 to 95 percent by weight of such an AN-S copolymer. If the proportion of the PVA-AN copolymer is less than 5 percent by weight, leave the fibers are difficult to fibrillate by milling and have only a low degree of hydrophilicity. if If such a synthetic paper stock is mixed with wood pulp for paper manufacture, none is obtained Paper with excellent physical properties. On the other hand, if the proportion of the PVA-AN graft copolymer on the mixture exceeds 40 percent by weight, the water resistance and the Dimensional stability of the paper against moisture.

It is not desirable that the proportion of the AN-S copolymer is less than 60 percent by weight,

because then the coagulability of the fibers in the precipitation bath is reduced. The polymer mixture for production of the synthetic paper stock is not limited to these two copolymers. Rather, the mixture can also unreacted PVA and AN polymer, which are by-products in the graft copolymerization arise, and also contain another polymer of acrylonitrile.

Most of the unreacted PVA is used in the fiber and paper stock manufacturing process Removed form of an aqueous slurry. However, the proportion of PVA should be in the originally manufactured Polymer mixture does not exceed 23 percent by weight. If the percentage of unreacted PVA is more than 23 percent by weight, it will result in foaming in the aqueous slurry.

The proportion of AN polymer in the polymer mixture should not exceed 35 percent by weight. if If the AN polymer content is flour than 35 percent by weight, excessive fibrillation occurs.

As far as the addition of an AN polymer to the polymer mixture is concerned, a separate one can be used use produced linear polymer. A polymer with a molecular weight of about 20,000 to 100,000 is preferred. The polymer can contain units of the monomeric vinyl compounds specified above, which can be used for copolymerization, as units of copolymerizable constituents in Contain amounts not exceeding 40 mole percent.

Regarding the process for the production of the synthetic paper stock from the polymer mixture described above the grinding of fibers made from the mixture and a method for direct Manufacture of paper stock from the polymer mixture.

The methods of making fibers include relaxation spinning and emulsion relaxation spinning, also the usual spinning rivet testicles such as wet spinning, dry spinning and phase separation spinning. Of these methods, the wet spinning method is particularly preferred. Another explanation the wet spinning method! below.

The mixture of the PVA-AN copolymer and the AN-S copolymer is dissolved in a solvent, such as dimethyl sulfoxide. solved. This solution is then in a conventional manner by wet spinning aqueous spinning bath, e.g. B. an aqueous solution of dimethyl sulfoxide, the maximum 80 percent by weight of dimethyl sulfoxide contains, processed to a non-stretched, water-containing gel thread. The undrawn thread can stretched in a hot water bath or in a steam atmosphere. It can also be stretched Threads are subjected to a heat treatment to fix their length, or they can be placed in hot In water or in water vapor.

The draw ratio is preferably more than 3.0; however, the invention is not at this value limited. The use of undrawn filaments does not detract from the objects of the invention. If however, when using undrawn threads, care must be taken in handling them because undrawn Threads have a low strength.

In the heat treatment for relaxation, the relaxation ratio is preferably more than 45%; however, this is not intended to limit the scope of the invention. After such a procedure one can easily get one produce fine paper stock with good displaceability. When the draw ratio is no longer bi is more than 3.0, the thread exposed to such a heat treatment is more likely to be cut during the painting process as fibrillicrt. But if the milling is carried out without subjecting the thread to the heat treatment The objectives of the invention can also be achieved at a stretching ratio of not more than 3.0 will.

It is important that the above-mentioned fiber material consists of a hydrophilic component (the PVA graft copolymer) and a hydrophobic component (the AN-S copolymer), and that the hydrophilic Component is dispersed in the hydrophobic component and in the form of an independent phase in the Direction of the fiber axis is present.

Such a fiber material can be easily fibrillated by grinding, and accordingly a ϊ Paper pulp or a paper pulp-like material excellent in hydrophilicity and dispersibility in Water and excellent self-adhesive properties.

The threads are then cut into staple fibers with lengths of 1.0 to 25 mm.

Instead of being subjected to the heat treatment described above before cutting, /, the Fibers are also subjected to heat treatment in hot water or in a water vapor atmosphere will. In this case, it is desirable that the treatment temperature be in the range of 90 to 120 ° C and the Treatment time ranges from 30 seconds to 8 minutes; however, the invention is not limited to this.

The fibers obtained by the above process can be easily collected by the same method of milling fibrillate, which is commonly applied to wood pulp, and can make a paper pulp of excellent quality Dispersibility in water can be processed.

The staple fibers described above can be in an aqueous dispersion with a concentration of 1 to 20 percent by weight transferred and in conventional grinding devices, such as Hollander, cone pulp mills, FPI mills and ball mills to be subjected to the milling treatment.

The synthetic fibers produced according to the invention have a self-binding microfibril structure. The paper pulp particles are intertwined by microfibrils. Each of these fibers can be in their smallest dimension have a diameter of 0.01 to 5 μm, preferably 0.05 to 3.0 μm. the The length of the individual fibers can be more than 5 times, preferably 20 times, the mean diameter be.

The synthetic paper stock can exclusively or partially have a latent microfibril structure. The term "latent microfibril structure" refers to fibrous material that is itself according to the invention has been obtained, or on fiber material that has been partially comminuted in the grinding process and in In the form of microfibrils. The latent microfibril structure is a precursor that emerges when sufficient Grinding completely converts into microfibrils. When grinding with conventional grinding devices is done to such an extent that the milled fiber material is used to produce a paper-like one Sheet, the greater part of the paper stock has a microfibril structure. When grinding can be as by-products Powdery, tiny particles are formed that are smaller than the above-mentioned microfibrils, this one however, are not essential to the invention.

When the smallest dimension of the above microfibrils does not meet the requirement that the diameter at least 0.01 μπι and the length is more than 5 times the mean diameter, the interweaving the paper stock particles impaired, which affects the strength and texture of the paper.

Since the paper stock according to the invention contains microfibrils and latent microfibrils, can be Control the grinding degree as desired by changing the grinding conditions. You also get a paper of excellent wet strength without any additives such as binders since the microfibrils have self-adhesive properties exhibit.

The structure of the synthetic paper stock produced according to the invention can be characterized by a freeness which is determined according to the Japanese industrial standard JIS-P-8182 using the "Canadian Standard Freeness" testing machine. The freeness of the paper stock according to the invention should be in the range from 50 to 600 cm ^J , preferably in the range from 100 to 400 cm K. If the freeness is less than 50 cm ³ , the tensile strength of the resulting paper is reduced and the speed of papermaking is so reduced that papermaking becomes practically impossible. On the other hand, if the freeness ^{exceeds 600 cm 3} , the pulp loses its ability to be made into paper, and paper having good texture, surface uniformity and good physical properties cannot be obtained.

The transparent paper according to the invention is obtained by using a sheet which, on a dry basis, 6 to 60 parts by weight of the synthetic paper stock described above and 94 to 40 parts by weight of natural Contains paper pulp (Zeiistoif), a transparency treatment under the action of moisture, Subjected to heat and pressure.

Wood pulp is particularly preferred as the natural paper stock; however, you can also use paper stock, made from bast fibers or animal fibers.

If the proportion of synthetic paper stock is less than 6 parts by weight, that is sufficient The raw sheet obtained does not meet the practical requirements for transparency, wet strength, tensile strength, and folding strength and dimensional stability although these properties of the raw sheet compared to one transparent base paper that is only made from conventional natural pulp are improved. if on the other hand, the proportion of the synthetic pulp exceeds 60 parts by weight, the mechanical Uneven strength, in particular tear strength and folding strength are reduced. Preferably the paper is made from 10 to 50 parts by weight of synthetic paper stock and 90 to 50 parts by weight of natural paper Paper pulp made

The synthetic and natural paper stock are mixed with one another in the above proportions mixed and processed into paper sheets by the conventional wet process in the paper machine In papermaking, the usual additives, such as sizing agents, fixing agents, release agents, and antistatic agents can be used Agents, fillers and dyes, can be added.

In the papermaking process, starch, polyvinyl alcohol, carboxymethyl cellulose, sodium algae

nat, solutions or emulsions of synthetic resins or conventional transparencies with the Dip roller, by impregnation or by coating can be applied.

The basis weight of the paper obtained in this way can be controlled ^{in the range from 25 to 200 g / m 2;} however, the invention is not limited thereto.

According to the invention it is possible to achieve high transparency without using a highly milled paper stock, as is usually used for the production of transparent paper. Heretofore, it has been necessary to use a highly milled paper stock with a CSF (Canadian Standard Freeness) freeness of 50 to 150 cm ^-1 in order to produce the usual transparent paper. According to the invention, however, excellent transparency can be achieved with paper stock which has been ground in the usual manner or only slightly. Therefore, the disadvantages associated with the use of highly milled natural pulp, such as a decrease in paper making speed, deterioration in physical properties such as roominess, tear strength and folding strength, and formation of bubbles can be avoided by using the invention.

The paper sheet thus obtained is then made transparent by moistening it to a moisture content in the range of 5 to 40% and then passing it through a press with a surface temperature above 130 ^° C., where pressure and heat are applied. The moisture content is calculated according to the following equation:

c u. i. ·. ui. Weight of the sheet containing enes in the water _inn

Moisture content = ——— ■ X 100 Weight of the hydrous sheet

If the moisture content is less than 5%, a uniformly transparent sheet cannot be obtained produce. If the moisture content is more than 40%, the mechanical strength of the arch will decrease reduced so that it adheres to the platen and difficulties such. B. by breakage, makes. To the Typical wetting methods include a method of coating with water using a coating device and a method of spraying with water and the so-called electrostatic wetting method. Various additives such as sizing agents, release agents, antistatic agents, dyes and transparencies to which water is added.

Suitable devices, such as a supercalender and a machine calender, can be used for pressure treatment. use a device with two rollers forming a nip or a hot press.

During transparentization with such devices, the sheet is pressed at least once in a printing apparatus having a surface temperature of 130 ⁰ C or more, whereby the desired transparency of the Bogtms is achieved. However, since the synthetic polymer constituting the synthetic pulp, decompose at about 250 ⁰ C, one must take care to ensure that the temperature of the sheet not exceeding 250 ° C increases. The pressure applied to the sheet is controlled as desired depending on the thickness of the sheet, the mixing ratio of the two types of paper, and the dampening conditions. Usually it can range from about 980 to 4900 N / cm, preferably from about 1176 to 3920 N / cm.

The transparent paper according to the invention offers various advantages over that described below conventional transparent paper, such as glassine paper or made of poly - ^ - olefin fibers and wood pulp made transparent paper.

The synthetic paper stock described above can be evenly distributed in the form of microfibrils, which have numerous microvoids and have hydrophilic residues themselves. Hence it works in the arch contained water not only for the natural paper stock, but also for the synthetic paper stock as Plasticizers. When the sheet is subjected to the heat and pressure treatment, it escapes inside it contained water together with the air that fills the micro-cavities, whereby one of the polymers, from which the synthetic paper stock is made, develops its own clarity and the paper an excellent one Gaining transparency.

The equilibrium moisture content (at 20 ^° C. and 60% relative humidity) of the untreated paper

according to the invention varies depending on the proportion of synthetic paper stock and is e.g. B. 6% if that

Paper consists of 10 parts by weight of synthetic paper pulp and 90 parts by weight of natural pulp, while

it is only 4% if the paper is made of 60% by weight synthetic and 40% by weight

natural paper stock. If you want to achieve the desired transparency, there is one

Relationship between the proportion of synthetic paper stock and the moisture content that by a

Increasing the proportion of synthetic paper stock decreases the moisture content. So if the The proportion of synthetic paper stock is 60%, it is sufficient to achieve the intended effect that the

Moisture content is at least 5%. If the proportion of synthetic paper stock is 10%, the moisture content is preferably more than 20%.

As is apparent from the above description, the transparent paper according to the invention offers the following advantages:

(a) It has a uniform and high transparency.

(b) It has excellent physical properties such as tensile strength and folding strength.

(c) It has excellent moisture or water resistance, eliminating disadvantages such as curling, Stretching and curling, can be avoided.

(d) Bubbling upon heating can be avoided.

(e) It is suitable for various purposes, such as offset printing and postpress.
(0 It also offers various advantages in production, such as increased papermaking speed.

speed, a reduction in the grinding treatment required, and a simplification of the transparency treatment.

The invention encompasses not only completely transparent but also partially transparent paper.

The transparency of the paper can be controlled according to its purpose. She is z. B. in generally set to more than 50% if the paper is to serve as a template for reproduction. For Drawing paper or curve paper, the transparencies / are set to more than 60%. The Set transparency if the paper is to be used as glassine paper.

The transparency is calculated according to the following equation:

Transparency = 100 - (value of opacity),

where the value of the opaque wedge with the Hunter reflectometer according to JIS test standard P-8138 is determined.

In the following examples, values and parts refer to the, unless otherwise specified Weight.

example 1

A PVA-AN graft copolymer with a ratio of PVA to AN of 50:50 is grafted on from AN to PVA, which has a degree of polymerisation of 1400, according to the usual radical chain polymerisation method using a persulfate salt as a catalyst.

An AN-S copolymer having a ratio of AN to styrene of 24: 76 and an intrisic viscosity of 0.54 (determined in methyl ethyl ketone at 30 ⁰ C) is prepared by a conventional suspension polymerization method.

1 part by weight of the PVA-AN graft copolymer and 4 parts by weight of the AN-S copolymer are in 15 parts by weight of dimethyl sulfoxide (hereinafter referred to as "DMSO") to a 25 percent spinning solution »Resolved.

This solution is wet spun from a spinneret with a diameter of 0.08 mm into a bath of 45% water and 55% DMSO _1, and an endless thread with a titer of 7 denier and a PVA content of 10% is obtained. The draw ratio is 2. This thread is cut into staple fibers with lengths of about 10 mm, and the fibers are then ground in a single-disk pulp mill at a pulp concentration of 3% and a distance of 50 μΐη to a synthetic paper pulp (A) CSF freeness is 200 cm ³ . The mean diameter of the fibrils is 8 μm, the minimum diameter of a fibril is 0.5 μm and the ratio of length to mean diameter is about 50.

Bleached hardwood kraft pulp (L) with a freeness of 480 cm ³ , bleached softwood pulp (N) with a freeness of 350 cm x ¹ , and strongly ground, bleached softwood kraft pulp (N ') with a freeness of 100 cm ^J and strongly ground, bleached hardwood kraft pulp (L ') with a freeness of 120 cm ³ . The above synthetic paper stock (A) and the pulps (L), (N), (L ') and (N') are prepared in the compositions given in Table I with the aid of a manually operated paper machine (with a metal wire mesh with a mesh size of 177 μΐη), processed into paper.

For comparison purposes, a bleached Nadelhoiz kraft pulp (N ') with a freeness of 100 cm ³ and a bleached hardwood kraft pulp (L') with a freeness of 120 cm ^{3 are} mixed with the above synthetic paper pulp (A) and among those in Table I processed into a sheet of paper.

The moisture contents of the dry sheets thus obtained are controlled according to Table I by applying water to the sheets with a wire-wound coating rod. Then, the arc of the Transparentmachungsbehandlung be subjected, by a total of four times by interchanging the underside to the top side of each sheet through the nip of a nip roll having an elastic roll and a hard chrome-plated metal roll (surface temperature 150 ⁰ C) under a linear pressure of 1323 N / cm. Various characteristic values of the transparent sheets obtained in this way are shown in the table! specified. The transparent paper sheets obtained according to the invention outperform the comparison paper in suitability for paper production, transparency, physical properties and further processability. The transparent paper according to the invention has well balanced properties.

'

Example 2

Two types of threads with PVA contents of 30% and 10% are produced by the spinning method of Example 1 from a 25 percent solution of a mixture of 1 part by weight of PVA-A N copolymer, produced by grafting AN onto PVA with a degree of polymerization of 1800 determined by a conventional radical chain polymerization method using a persulfate salt as a catalyst at a ratio of PVA to AN of 80:20, with 1.67 or 7 parts by weight of an AN-S copolymer with an intrinsic viscosity of 0.65 at 30 ^° C. in methyl ethyl ketone, prepared by a conventional suspension polymerization method with a ratio of AN to styrene of 30:70, obtained in DMSO. The draw ratio is 3.5 and the filaments of both types have a denier of 5. The filaments are cut into staple fibers with lengths of about 3 mm and the staple fibers are then ground according to Example 1, whereby two types of synthetic paper stock are obtained. One synthetic paper stock (B) has a PVA content of 30% and a freeness of 195 cm ³ , the other synthetic paper stock (C) has a PVA content of 10%

and a freeness of 240 cm ³ .

The mean diameter of the fibrils with the PVA content of 30% is 2 μm, the minimum diameter of the individual fibrils 0.2 μπι and the ratio of length to average diameter about 90, while at the fibrils with the PVA content of 10%, the mean diameter 4 μm, the minimum diameter of a Fibril 0.3 μm and the ratio of length to average diameter is about 70.

Separately from this, a bleached softwood kraft pulp (N ") with a freeness of 280 cm ^J and a bleached hardwood kraft pulp (L") with a freeness of 450 cm ^J are produced.

Under the conditions given in Table H, paper sheets according to Example 1 are made from the above specified synthetic paper stocks (B) and (C) and made from pulps (N ") and (L"). Of the The moisture content of this sheet is determined according to Table II in the same way as described in Example 1, set. Then the sheets are at a roller surface temperature of 140 ° C and a linear Pressure of 2156 N / cm sent a total of four times through the two-roll calender described in Example 1, where the sides (top and bottom) are swapped. The properties of the transparent one thus obtained Paper are shown in Table II.

Example 3

There are two types of threads with PVA contents of 7% and 20% according to that described in Example 1 Wet spinning method produced. A 25 percent solution of a polymer mixture is used as the starting solution in dimethyl sulfoxide. The polymer mixture consists of 1 part of a PVA-AN graft copolymer, produced after grafting AN onto PVA with a Polymcrisalionsgrad of 1100 according to a known one Free radical polymerization method using persulfate salt as catalyst at one ratio from PVA to AN of 60:40, and 7.57 or 2 parts of an AN-S copolymer with an intrinsic viscosity of 0.65, determined at 30 ° C in methyl ethyl ketone, prepared by a conventional bulk polymerization process with a ratio of AN to styrene of 20:80.

Both types of threads have the same Idene titre. The filaments are cut into staple fibers with lengths of about 5 mm and the staple fibers are then ground according to Example 1 into two types of synthetic paper stock. The synthetic paper stock (D) with the PVA content of 7% has a freeness of 230 cm ³ , while the other synthetic paper stock (E) with the PVA content of 20% has a freeness of 200 m ³ . The mean diameter of the fibrils with a PVA content of 7% is 13 μm, the minimum diameter of a fibril is 0.8 μm and the ratio of length to mean diameter is about 45, while the mean for fibrils with a PVA content of 20% Diameter 8 μm, the minimum diameter 0.5 μm and the ratio of length to mean diameter are approximately 55. Separately from this, the bleached softwood kraft pulp (N) described above and the bleached hardwood kraft pulp (L) are produced according to Example 1. The above synthetic paper pulps (D) and (E) and the pulps (N) and (L) are mixed in the proportions given in Table III and processed into dry paper sheets in a test Fourdrinier machine at a paper production speed of 20 m / min.

The moisture content of these sheets is determined as indicated in Table IU by coating with water with Adjusted with the help of a test coating device. Then the sheets go through four nips a supercalender with alternating cooled rolls with the highest surface temperature of 160 ° C and cotton-filled rollers and a linear pressure of 2156 N / cm. The properties of the transparent paper sheets thus obtained are shown in Table 111.

Comparative example 3

Transparent paper sheets are produced according to Examples 1 to 4, but with a commercially available one Paper stock which, instead of the synthetic paper stock (A) of Examples I to 4, is a commercially available one Contains paper stock made from poly-A-olefin fibers, and without regulating the humidity. The transparency of the so obtained transparent paper is only 60%. It also makes a considerable macroscopic effect Unevenness of transparency noticeable. Those according to Examples 1 to 4 and according to the comparative example The resulting paper sheets are examined for their printability with the offset press. The transparent ones Sheet of paper according to the example! ! to 4 show good ink receptivity and provide good ones Results when printing. In contrast, the one obtained after the comparative experiment shows a transparent one Paper has poor ink receptivity because of its poor water absorption and has microscopic white spots.

Example 4

A continuous thread of 7 denier with a PVA content of 7% is produced by the spinning process of Example 1 from a 25 percent solution of a polymer mixture in DMSO. The polymer mixture consists of 1 part PVA-AN graft copolymer, produced by grafting AN onto PVA with a degree of polymerization of 2600 according to a conventional radical chain polymerization method using persulfate salt as a catalyst at a ratio of PVA to AN of 30:70 and 3.29 Parts of AN-S copolymer with an intrinsic viscosity of 0.54, determined at 30 ° C. in methyl ethyl ketone, prepared by a conventional suspension polymerization process with a ratio of AN to styrene of 24:76. The thread obtained in this way is cut to staple lengths of about 10 mm, and the staple fibers are ground according to Example 1 to a synthetic paper stock (F) with a freeness of 280 cm ³ . The mean diameter of the fibrils is 13 μm, the minimum diameter of a fibril is 0.8 μm and the ratio of

Length to mean diameter about 45.

The bleached softwood kraft pulp (N) and the bleached hardwood kraft pulp (L) according to Example 1 are mixed with the synthetic paper stock (F) in the proportions given in Table IV. The mixed paper stock is in an experimental Fourdrinier machine at a speed of 20 m / min processed into two sheets of paper The moisture contents of the dry sheets are adjusted to the values given in Table IV specified values are set by applying the sheet to the test coating device with the aid of a connected spray humidifier with a 3 percent aqueous solution of glycerin as Plasticizers are sprayed. Then the sheets are fed through four nips of a supercalender, the one with alternating cooled rollers, the highest surface temperature of which is 150 ° C, and cotton-felt Is equipped with rollers that exert a linear pressure of no more than 1960 N / cm on the paper. the Properties of the transparent paper sheets obtained in this way are shown in Table IV produced transparent paper sheets have a good combination of excellent properties. in the In contrast, the transparent paper produced according to Comparative Experiment 4 shows due to its poor quality Dehydration capacity an undesirable structure and as a result of its poor tear and folding resistance poor processability in the supercalender. In addition, this paper shows poor absorption for printing ink in offset printing. This transparent paper also has corrugations.

Example 5

A continuous thread with a PVA content of 28% is produced by wet spinning a 25-percent solution of a polymer mixture in DMSO according to Example 1. The polymer mixture consists of 1 part of a reaction product, which has been prepared by grafting AN onto PVA with a degree of polymerization of 1800 according to a known radical chain polymerization process using persulfate salt as a catalyst, and 74 percent by weight of a PVA-AN copolymer (75:25) , 20 percent by weight of unreacted PVA and 6 percent by weight of homogeneous acrylonitrile polymer, and 1.7 parts of an AN-S copolymer (intrinsic viscosity 0.71, determined in methyl ethyl ketone at 3O ⁰ C), prepared according to a conventional Suspension polymerization method with a ratio of AN to styrene of 15:85. The thread thus obtained has a titer of 7 denier and is cut into staple fibers with a length of about 5 mm, which are then ground ^{according to Example 1 to a synthetic paper stock (G) with a freeness of 240 cm 3.} The mean diameter of the fibrils is 4 μm, the minimum diameter of a fibril is 0.3 μm and the ratio of length to mean diameter is about 70.

Separately from this, a bleached softwood kraft pulp (N '") with a freeness of 550 cm ³ and a bleached hardwood pulp (L'") with a freeness of 620 cm ¹ are produced. The above synthetic paper stock (G) and the pulps (N '") and (L'") are mixed and processed into paper sheets under the conditions given in Table V. As a control, a sheet is used which, under the conditions specified in Table V, has only been produced from natural pulps (N '") and (L'").

The moisture contents of the paper sheets obtained in this way are regulated as indicated in Table V, by the sheets with the help of a wire-wrapped coating rod on one side with the help of a 0.3 percent aqueous solution containing sodium chloride as an antistatic agent. then the sheets are fed through a two-roll calender four times under a linear pressure of 2058 N / cm, which has an elastic roller and a hard chrome-plated metal roller (surface temperature 150 ° C), whereby the two sides of the arc are reversed. The transparent paper sheets thus obtained have the properties given in Table V.

The transparent paper sheets obtained in this example are the same as those in the comparative example is superior in terms of transparency, physical properties and further processability. the Properties of the transparent paper sheets produced according to the invention even exceed those of Gassin paper.

Example 6

A continuous thread with a PVA content of 10% is produced by wet spinning a 25% solution of a polymer mixture in DMSO according to Example 1. The polymer mixture consists of 1 part of PVA-AN graft copolymer, produced by grafting AN onto PVA with a degree of polymerization of 800 according to a conventional radical chain polymerization process using persulfate salt as a catalyst at a ratio of PVA to AN of 40:60, and 3 parts of AN -S copolymer with an intrinsic viscosity of 0.75, determined in methyl ethyl ketone at 30 ^° C., and a ratio of AN to styrene of 20:80. made by a conventional suspension polymerization process. The draw ratio is 2.0.

The thread has a titer of 10 denier and is cut into staple lengths of about 5 mm. The staple fibers are then ground according to Example 1 to a synthetic paper stock (H) with a freeness of 260 cm ^3. The mean diameter of the fibrils is 7 μm, the minimum diameter of a fibril is 0.5 μm and the ratio of length to mean diameter is about 50.

The same formed softwood kraft pulp (N '") and bleached hardwood kraft pulp are produced (L '") prepared as in Example 5.

The above synthetic paper stock and the pulps (N '") and (L'") are in the b5 given in Table VI Mixing ratios mixed and in a technical Fourdrinier machine with a 1975 mm wide Wire mesh fabric processed into three sheets of paper at a speed of 50 m / min.

As a control, a sheet of paper is made in the manner described above only from the wood pulps (N '") and

(L '") produced.

The moisture contents of the paper sheets are set according to Table Vf by using the sheet a commercially available stick applicator coated with a 0.2 percent aqueous solution, the one Commercially available wax emulsion contains as a release agent. Then each sheet is fed through 16 nips Supercalender guided: that with alternating chilled wakes with a highest surface temperature vcn 160 ° C and cotton-filled rollers that have a linear pressure of no more than 3920 N / cm exercise. The properties of the transparent paper thus obtained are shown in Table VI.

The transparent paper sheets of this example show excellent transparency and combination of properties with increasing synthetic pulp content, even if the moisture content is relatively low. In contrast, the comparison sheet made only from natural cellulose has a insufficient transparency even though it has been brought to a high moisture content

Table 1

Papermaking Resin glue Talc ¹ ), Oxidized Dehydration texture Surfaces Paper stock % Stürkelcim- ization weight together layer ² ), speed of paper, setting on g / m ² age ³ ), g / m ² Dry basis sec / 101

A: N: L

comparison

1-1 O: 30: 70 comparison 80: 20: 0 no 0 0 1-2 5:50:45 1-3 A: N ': L' no 0 1.2 3example
1-1 7.5: 50: 42.5 0:80:20 no 0 1.2 1-2 10:50:40 1-4 (Continuation) no 0 1.2 1-3 25:30:45 Table 1 Yes 6.0 0 1-4 30:30:40 no 0 0 1-5 30:30:40 Yes 5.8 0 1-6 30:30:40 no 0 1.0 1-7 60:40: 0 no 0 0 no 0 0 no 0 0

3.0 3.1

3.2 3.3 4.2 4.1 4.8 4.5 6.2

16.5

35.2

Well 60 Well 30th Well 40 Well 30th Well 40 Well 60 Well 60 Well 60 Well 80 not 60 So good

bad 60

Properties of the transparent paper Moisture · «- Mass Trans

salary.

density, g / cm '

parence ⁴ ),

Liifldurchliissigkit ⁵ ), see / 100 cm ^J

Tear length ⁶ ), km

Tear factor ⁷ )

comparison

1-1 30.3 .10 39.1 150 7.63 54 1-2 28.5 , 08 51.2 170 7.31 50 ispiel
1-1 22.5 .07 63.4 780 7.34 48 1-2 31.6 , 08 66.1 1 230 7.42 48 1-3 24.3 , 09 79.8 3 480 7.16 44 1-4 18.1 .01 75.6 27 500 7.72 43 1-5 20.5 .07 75.3 24,000 6.85 47 1-6 17.2 1.05 77.9 35,000 7.23 42 1-7 9.8 3.98 71.3 30 600 8.01 39 ; r same
1-3 8.3 0.96 70.8 50 800 7.32 15th 1-4 25.4 1.18 68.9 16,000 8.17 40

10

Table I (continued)

Properties of the transparent paper

Falzfestig- tear length ¹ *) extension ¹ ")

speed ⁸ ) after being put back into water

WITH wetting. %

km

Appearance

Offset pressureUbarkcit Ripple acceptance not Print color Well So good not Well So good Well Well Well Well Well Well Well Well Well Well Well Well Well Well

comparison 380 1-1 410 1-2 example 420 1-1 450 1-2 2450 1-3 2700 1-4 3100 1-5 5600 1-6 2500 1-7 comparison 500 1-3 8500 1-4

0.54
0.71

0.89
0.91

1.95
2.45
2.16
1.98
2.75

3.02
0.74

1.93 1.68

1.51 1.03 0.65 0.38 0.21 0.48 0.11

0.09 2.58

not good not good

good good good good good good good

Well

uneven,
Blisters, rough

not

so good

Well

Well
bad

Remarks:

1) Talc as filler,%:

Ash content of the dry paper, determined according to the Japanese industrial standard JIS P-8128.

2) Oxidized starch glue layer:

Weight per unit area of the layer in g / cm ² on a dry basis.

3) dehydration speed:

For the dehydration of iOI paper slipper dispersion on a Mctalldrahlnelz (mesh size 177 μΐη) one of Hand operated paper machine with a width of 20 cm and a length of 25 cm required time.

4) Transparency,% =

100 - opacity value determined with the Hunter reflectometer (ILP-8138).

5) Air permeability determined with the high pressure densometer according to Gurlcy (ASTM test standard D 726-58. Method B).

6) Tear length determined in accordance with JIS P-8113.

7) Tear factor, determined according to) 1S P-8116. ⁴⁰

8) Fold strength, determined according to MIT in accordance with JlS P-8115.

9) tear length, km =

Tensile strength of the rewetted paper, km

Basis weight (g / m ² ) on a dry basis x paper width

x 1000

wherein the tensile strength of the rebenel / .len paper is determined in accordance with) 1S P-81 Jb, the basis weight is given on a dry basis in accordance with JIS P-8111, and the paper width is 15 mm as shown in FIG IS P-8135 is defined.
10) The expansion in water is determined with a fennel expansion eater after immersing the sheet in water at 20 ° C. for 5 minutes.

The comments also apply to Tables II to VI. Table II

Papermaking Resin glue Talc, Oxidized Dehydration Paper pulp % Starch glue ization gather together- layer, speed setting on g / m ² age, Dry basis sec / 101

texture

Basis weight
of paper,
g / m ²

example

2-2
comparison

B: N ": L"
30:55:15

C: N ": L"
30:55:15

B: C: N'7L "
0:55:45

no

Yes

Yes

5 ,!
0

5.1

1.0

6.5

6.7

4.8

Well

Well

Well

40
40

40

Table II (continued)

Properties of the transparent paper

Humidity, mass, trans, air permeability, density. parence. casual wedge. % g /; m ^s % sec / 100 cm ³

Tear length. Tear factor

km

example

2-1 17.8 2-2 16.5 comparison 2 20.5 Table II (continued)

1.05 1.04

1.12

80.8 78.5

51.0 7200
9200

1200

8.30 7.62

7.92

43 44

49

Properties of the transparent paper

Rebate wedge Tear length Extension Appearance

after

benet / .ung.

km

in water. Offset printability

Ink ripple

acceptance

example

2-1
2-2

comparison
2

Table III

3400
2700

1200

1.4 2.1

0.9

0.95 0.26

2.05 good
Well

not
so good

good Good

Well

good Good

not so good

Papermaking

Paper stock together
section on
Dry basis

Resin glue

Talc. Oxidized
Starch glue layer,
g / m '

texture

Basis weight of the paper, g / m ²

example

3-1
3-2

D: N: L
25: 50: 25
E: N: L
25: 50: 25

Yes / Yes

0 0 good good

40 40

Table 111 (continued)

Properties of the transparent paper

Fcuchtigkcits- Mass Trans-

content, density. parence.

density. g / cm '

l. air flow

liissigkcii,

sec / IOOcm '

Tear length,

km

Length Width

Tear factor length / width

example

3-1
3-2

24.0
16.0

1.13 1.15

72.0

74.1

7.51 / 6.03 7.82 / 6.25

42/45 41/43

Table III (continued)

Properties of the transparent paper Stretch appearance Dehydration Offselprintability texture Ripple Kciülängc after in water, ization Printing inks Rewetting, broad speed adoption km age Length Width Well example 0.46 good Well Well 3-1 2.0 / 1.5 0.53 good Well 3-2 2.4 / 1.8 Table IV Area Papermaking Talc, oxidized weight Paper stock har / Ieim % Strength cim- of paper, together layer. g / m ² setting on g / m ² Dry basis

Q: N: L

example

4-1 8: 20:72 Yes 6.2 1.5 Well Well 50 4-2 15:20:65 Yes 6.4 1.5 Well Well 50 comparison 4th 80: 20: 0 Yes 6.1 1.5 bad scaly 50

Note: dehydration on the wire mesh of the experimental Fourdrinier machine. Table IV (continued)

Properties of the transparent paper Crowds
density,
g / cm ' Trans
parence.
% Tear length
after again
wetting, km
Length Width Air flow
casual wedge,
lake / 100 cm ' Tear length,
km
Length Width Tear factor
Length Width Moisture
salary,
% example 1.12 64.2 15,000 6.83 / 5.12 38/31 4-1 22nd 1.08 67.8 18 300 7.04 / 5.54 37/32 4-2 22nd comparison 1.09 75.3 20 400 7.54 / 5.38 19/16 4th 22nd Table IV (continued) Properties of the transparent paper Folding strength.
Length Width Stretch appearance
in water.
%
(Broad) Offset printability
Ink ripple
assumed

example

4-1 390/195 4-2 480/310 comparison 4th 100/51

0.82 / 0.57 1.41 / 0.92

2.73 / 1.54

1.54 1.37

0.64

good Good

Curl

Well
Well

not
so good

good Good

Well

13th

Table V

Papermaking Resin Clim Talc. Oxidized Mass Dehydral piers Tear length expansion speed Dchydrali- speed texture Surfaces not U Paper slipper "/ ο density. Starch glue Trans after re- in water. age Starch glue digkcit. weight So good egg / collectcn- g / eni ' layer. godparents /. wetting. "/, I layer. scc / 101 of the paper. sel / .ung on g / m- ' km g / m ² g / m ² Well 1 Dry basis 1.05 1.9 Well I. G: N '": L'" 55.1 0.61 1.62 comparison No no 1.12 2.1 3.5 Well 30th I * 5 0:70:30 1.14 82.4 3.8 Surfaces : ■ '■'! example No no 2.0 86.9 1.15 1.10 Well 30th weight I. 5-1 20:70:10 No no 1.9 1.42 0.99 Well 30th of paper, v '.'
% 5-2 30:70: 0 Properties of the transparent paper l.ufldurch- g / m ² I. Table V (continued) Properties of the transparent pa Folding strength liquidity. Ä Moisture Shark / glue talc. Oxidized sec / 100 cm ¹ Tear length. Kcißfiikior salary. % km k % 210 ψ comparison 25th 850 1450 7.32 54.1 5 6500 χ. example 25th 8.10 48.2 5-1 25th 1020 8.15 45.3 5-2 Table V (continued) 1300 Appearance H Papermaking Offset printability Paper pulp Ink ripple Together assumed setting on Well 3 comparison Dry base 5 Well Jt Well ¹ L example Well (
a * ι 5-1 Well S. 5-2 Well I. Table Vl texture

comparison

b example

b-1 b-2 b-3

0:40:60

15:40:45 JO: 40: 30 b0: 40: 0

no

no no no

5.2

5.5
5.6

5.4

1.8

1.8 1.8 1.8

Well

150

Well 150 Well 150 Well 150

14th

Table VI (continuation)

Glossy transparent paper

l'Leuchtigkcits- Mass Trans

parence.

42.1

66.5 68.2 74.5

salary,
"/ (I density
g / cm ' comparison 6th 28 1.05 example 6-1
6-2
6-3 22nd
18th
12th 1.12
1.16
1.08

l.iiftdurchlüssigkeii, see / 1 (K) cm '

RciUUingc.

km

Length Width

6.51 / 4.32

b.98 / 5.42
6.85 / 5.59
7.52 / 5.83

Tear factor
Length Width

45.1 / 39.3

43.2 / 28.5
41.3 / 37.4
37.5 / 34.1 ₁₅

Tabeiie Vi (continued)

Properties of the transparent paper Fold strength, tear length expansion Length / width after back in water,

wetting, km%

Length Width Appearance offset printability

Ink ripple
assumed

comparison
6th

example

820/560

2040/1750
2130/1810
2060/1540

0.62 / 0.42

1.02 / 0.73 1.35 / 0.97 1.67 / 1.02

1.84

1.35 1.21 0.78 bad
transparency

Well
Well
Well

Well

Well
Well
Well

Well

Well
Well
Well

15th

Claims (1)

Patent claims: 1. Transparent paper, characterized in that it has been produced by moistening a fiber mass in the form of a sheet up to a moisture content of 5 to 40% and then pressing the moistened flat, formed with a pressing device at a press surface temperature of at least 130 ⁰ C, wherein the pulp is made on a dry basis a) 6 to 60 parts by weight of synthetic paper made from a polymer mixture which to 5 to 40 percent by weight of a copolymer of polyvinyl alcohol and acrylonitrile, in which the ίο Polyvinyl alcohol is chemically bound to the acrylonitrile, and in which the content of polymerized Polyvinyl alcohol is 20 to 80 percent by weight, and 60 to 95 percent by weight of a copolymer of acrylonitrile and styrene with an acrylonitrile content from 5 to 45 percent by weight, and b) 94 to 40 parts by weight of natural pulp