DE2512921A1 - PROCESS FOR THE MANUFACTURING OF PAPER FILMS BONDED TO FILMS OF POLYMERIC MATERIAL - Google Patents

Description

The present invention relates to a new method for the production of cellulose paper films bonded to a film made of a thermoplastic polymeric material as well as on the bonded foils obtained by this process.

In recent years, it has been common to use paper foils bonded with plastic films in the packaging field.
These papers are obtained by joining, usually under pressure, a sheet of paper to a film of polymeric material after treating it with an adhesive, or by treating one or both components with an electrical coronary discharge to improve their mutual adhesion. The process is quite complicated and requires the separation of the manufacturing equipment sou / ohl for the paper foil as well

509841/0862

for the polymer film. Because of the great difficulty in the production of films from high molecular weight polymers by extrusion mar this process continues to use limited by low molecular weight polymers while still having films with poor mechanical properties and got random "Grenzwerw" properties.

Most commonly used in the known technique consists in the management of a surface-treated with a suitable adhesive Paper film to the head of a polymeric film extruder, which is the continuous paper film with a polymeric Covered film, which is firmly connected to this - by pressure. The device shown in Fig. 1 illustrates this method, In this drawing, (i) means the feeding roll of the paper film, (2) is the container containing the adhesive, (3) the dryer, (4) the extruder, (5) the polymeric film, (6) the Rollers for compressing and cooling the bonded product, and (7) is the winding roll of the finished product.

Such a method brings due to the low extrusion speed of the film and the relative ease with which the latter tears because of its minimal thickness and the paper leaves uncovered, with considerable disadvantages. These 'disadvantages are strengthened whenever multilayer connected products, e.g. so-called "sandwich" structures, are to be manufactured in which the polymer film is enclosed between two sheets of paper.

509841/0862

It has now been found that a rapid and inexpensive process can be used to bond a thermoplastic polymer film Cellulose paper with superior properties compared to the previous ones known materials can be prepared by using this polymeric material in the form of fibrils, which in an aqueous Medium are dispersed.

The term "fibril" as used herein means hair fibers or fibrous products with a length between 1-50 mm, an average diameter between 1-400 microns and one specific surface area over 1 m / g.

These fibrils known in the art can be made by various methods and are commonly used in the manufacture used by synthetic paper. One method of making fibrils from a polyolefinic material is e.g. described in the Italian patent specification 947 919.

In this process, a solution of the olefin polymer is used a temperature above the boiling point of the solvent under normal "conditions and under autogenous pressure or a extruded above this pressure into a zone of lower pressure and then in an at least expanded state by a high velocity jet of a flowable material at a temperature below that of the solution in a given one Made angle to the extrusion direction of the solution.

Other methods of making fibrils of synthetic polymers that can be used to make the compounds of the present invention Films are suitable, for example, in U.S. Patents 2,999,788 and 3,402,231, British Patent 1,262,531

509841/0862

- 4 and DT-OS 1 951 576 urri OAS 1 290 040.

The aim of the present invention is therefore to provide a method for producing composite structures from cellulose paper with films of a thermoplastic polymeric material characterized in that one

(a) a film of at least two superimposed fiber

-en
like layer / forms, which at least mainly consist of cellulosic fibers or fibrils of synthetic thermoplastic polymers, obtained by successive layer formation or stratification of aqueous pulps or dispersions of these fibers or fibrils;

(b) the water content of the film by suction and / or compression reduced to an amount between 30-80 wt .- ^;

(c) the film to a moisture content below 0.5 wt .- / O dries; and

(d) the film to a temperature above the softening temperature of the thermoplastic polymer heated under pressure.

Between steps (b) and (c) there may be a cold compression step of the film can be switched on when printing between 50-150 kg / cm, the compression e.g. between "wet" - Rolling or pressing can be done if you want more compact papers or a lower moisture content before drying want.

509841/0862

To produce the fibrous film according to step (a), the fibrils can be made from any synthetic thermoplastic polymer with a softening temperature not exceeding 250 C. can be used in the form of a pulp or an aqueous dispersion. Suitable thermoplastic polymers are e.g. in particular polyolefins, in particular low and high density polyethylene, polypropylene, which consists mainly of isotactic macromolecules, ethylene / propylene copolymers with a predominant one Content of propylene, further polyamides, such as nylon 6, urinal polymers, such as polyvinyl chloride and polyvinyl acetate, polyacrylonitrile and the poloxymethylenes.

Whenever possible and especially to improve transparency and penetration of the plastic layer into the cellular " loose without reducing the "barriers" tenderness, are preferred Fibrils made from the same polymer, but with different ones uses thermoplastic properties; For example, in the case of polyethylene fibrils, it is preferred to use "an aqueous dispersion of high dense polyethylene fibrils mixed with low-density polyethylene fibrils ibrilen to use.

It can also be aqueous dispersions (or pulps) of different thermoplastic polymers can be used provided they are compatible with each other and have a sufficient one near softening temperature.

In the above-mentioned dispersions and cellulosic fibers in amounts not exceeding 10 wt -% be present of the total fiber weight..

509841/0862

In order to achieve the greatest possible coherence between the cellulose fiber layer and the layer of thermoplastic polymer in the finished product To achieve, it has been found to be effective in the film production in step (a) thermoplastic fibrils with a Size distribution in a wide range, preferably between 0.5-5 mm in terms of length and 3-60 / U in terms of diameter, to use.

Further preferred conditions for the production step (a) of the fibrous film are the use of pulp or aqueous Dispersions of thermoplastic fibrils with a fibril concentration, which is 1.5 to 2.5 times the concentration of cellulose fibers in the corresponding aqueous dispersions. So is on the contact surfaces of the film forming Layers the penetration ability of the fibers in a layer the fibers of the other layer are increased, which has significant advantages in terms of mutual adhesion between the thermoplastic phase and the cellulosic phase of the final product.

Overall, the process can be easily carried out using the methods commonly used in Paper mills used to carry out the devices used, the beating machines for the cellulose pulp and machines for production Drying and calendering of the paper foils include

The production of the multilayer fibrous sheet according to step (a) For example, by sequentially depositing the appropriate aqueous dispersions of the fibers on a filter section or by collecting the fibrous pulps on a common conveyor belt, directly from the corresponding aqueous Dispersions by forming machines connected in series

S09841 / 0862

flat or curved table, ujie this with the known papermaking processes is common.

Step (b) for eliminating the excess water from which Foil can be made by directing it over suction boxes and / or to / ischen squeeze rollers. This process favors that Phenomenon of the mutual penetration of the two layers due to the high water content of the pulp and is caused by the non-uniformity of the fiber sizes, especially the thermoplastic, facilitates.

The drying stage (c) of the film is expediently carried out between cylinders which are kept at increasing temperatures but below the softening temperature of the thermoplastic polymer present in the film; thereby drying has the water content of the film to not more than 0.5 wt -% decrease in order to avoid during the subsequent heating step (d) to high temperature, the formation of steam bubbles within the film, the heating step (d) is carried out under pressure, preferably. between 30-100 kg / cm between the rollers of a satin finishing machine and causes the thermoplastic fibrils to melt with the formation of a compact layer adhering to the cellulose layer,

If necessary, the composite material obtained by this last stage can, after cooling, be subjected to processes for surface treatment of the cellulose layer, such as calendering, coating, gluing, etc., as are customary for films made from cellulose paper.

509841/0862

The pulps or aqueous dispersions of the cellulosic soiuie thermoplastic fibrils necessary for the production of the starting films can contain additives such as dyes, pigments, inorganic fillers, agents against mildew, dispersants, etc. The dispersions of the cellulosic fibers can also contain other types of fibers in amounts not exceeding 10% by weight, based on the cellulose material, such as rayon fibers, cellulose acetate, nylon, polyvinyl alcohol, etc.

It is essential for the l / experienced that the fibrils of the thermoplastic Materials should be thoroughly and homogeneously dispersed in water to form homogeneous and uniform layers. In addition one usually has to use dispersants such as polyvinyl alcohol, anionic surfactants, Urea resins, etc., or the fibrils before use if necessary subject to a surface modification, the makes them dispersible in water. This modification can result in coating the fibrils with a dispersing agent in their Immersion in an aqueous solution of the dispersant and consist in their subsequent drying.

Such an experience in which the dispersing agents used

-Condensates consist of polyvinyl alcohol /! ^, Aliphatic aldehyde /,

is described in Italian patent application 19.329 A / 74.

The method according to the invention can be used to produce films made of plastic paper obtained in which the resistance to loosening or "puckering" of the individual layers is practically not measurable is because this resistance is greater than the tear strength of the Films themselves. A major advantage of the invention

509841/0862

251Z921

Method is that there are no limitations on the production speed of the films because of the durability of the cellulose carrier is not noticeably affected by the presence of the thermoplastic material in any stage of the process. So one can use the same cellulose preparations as well as the same procedural speeds occur as they are normally used for the production of foils from conventional paper, at these speeds are significantly above those that were applicable to the classic coupling or connection processes.

According to the invention, "sandwich" structures can of course also be used manufacture in which, for example, the thermoplastic polymeric material is in the form of a continuous film between two or several sheets of paper or cellulose cardboard is included.

Referring now to Figure 2, there is shown a complete diagram of the manufacture of a binary bonded film. The curvy ones included Molding container (i) and (2) the cellulose fiber pulp or the thermoplastic polymer fibril pulp; on the felt tape

(10) the cellulose fiber layer adheres and thereafter, through Overlay the layer of thermoplastic fiorile; (3) are the aspirators; (4) the "I \ laß" presses, (5) the sentences of the Drying cylinder, (6) the heated calendering device; (7) the chill rolls, (8) is the take-up reel for the connected Foil and (9) are the flow felt belts. In this diagram, the Position of the mold container can be reversed, achieving the same results without modifying the rest of the system.

509841/0862

- ίο -

Fig. 3 shows a complete diagram for the production of a ternary cellulose / thermoplastic material / cellulose structure »

Here mean (i) and (2) the Kundgen shaped container that the

-device containing cellulosic pulp »(3) is an inflow / with flat table containing the fibrils of thermoplastic material; (4) are the aspirators; (5) the 'wet ^' presses; (6) the sets of drying rollers; (7) the heated calender; (8) the cooling rollers; (9) on take-up spool and (10) the assembly lines.

The following examples illustrate the present invention, without restricting them.

In all examples, the olefin polymer fibers used were in accordance with the method of the above-mentioned Italian patent 947 919 has been produced.

Example j [

Manufacture of the polyolefin fibrils

A 50-1 autoclave equipped with a heating chamber and stirrer was used charged with 2.5 kg of high-density polymer (melt index = 5; temperature = 135 ° C.) and 1.5 g of kaolin together with 35 liters of η-hexane. The mixture was stirred at 180 ° C. until the polymer was dissolved in η-hexane. and one Total pressure (including excess nitrogen pressure) of 15 kg / cm heated. Under these conditions the mixture was released into the atmosphere through an annular nozzle 2 mm in diameter ejected and at a distance of about 1 mm from the nozzle outlet with a dry saturated steam jet a nozzle of 4 mm diameter at an angle of about 85 °

S09841 / 0862

to the direction of ejection of the mixture at an impact velocity of the water vapor of about 470 m / sec allowed to collide. The fibrous product thus obtained consisted of individual fibrils with a length between 0.5-5 mm, an average diameter between 15-45 microns, a specific one

2
Surface of 5 m / g and a kaolin content of about 30 wt .- ^ i.

Manufacture of the connected foil

Two pulps with the following composition were produced in two separate vats:

1) an aqueous mixture of 10 g / l cellulose with a degree of refinement SR = 35; . 16 wt -% of kaolin and 2 wt -% "Aquapel" (a glue for Cellulosefassrn).

2) an aqueous mixture of 15 g / l of the polyethylene fibrils prepared above, which before the addition by immersion in a aqueous solution of a dispersing agent composed of a polyvinyl alcohol / butyraldehyde condensate (4.2 aldehyde groups per 100 monomeric vinyl units) had been coated and 0.05 Gbui »- / 0 des The dispersant contained and then dried had been.

The two pulps were put into the corresponding "kurüigen" Molded container and delivered a film at a speed of 25 m / min, which consists of an approximately 2 mm thick layer of the cellulosic pulp and an overlying, e.g. 1 mm thick layer of the polyethylene fibril pulp.

509841/0862

After passing through three suction devices connected in series, the folia showed a water content of 80% by weight. By two wet pressing, which exerted a pressure of 50 kg / cm, the film was then passed to a series of drying cylinders 17 of which which were kept the first 1 on a rising temperature between 90 ° and 110 ⁰ C.; this dried the film to a residual moisture content of about 0.2 getu.-fc. The 17th cylinder was kept at a temperature of 125 C., which initiated a beginning melting of the outer polyethylene fibers.

Then, the film was passed through kept at 150 ^D C. embossing rollers, which exerted a pressure of 80 kg / cm, whereby the Fibrilschicht in a translucent and compact polyethylene film of about 20, u thickness was converted to the perfectly adhered to the cellulose film. The properties of this structure are summarized in Table 1.

Example 2_

A binary structure was produced by using as cellulose f A layer of cellulose pulp produced according to Example 1 and, as thermoplastic material, an aqueous mixture made of uncharged, high-density polyethylene fibrils with a melt index of 1.2 and a temperature of 135 ° C. with a Fiber length between 1.5-3.5 mm and a diameter between

15-40 / U and a specific surface area of 6 m / g, a fiber concentration of 20 g / l and a content of polyvinyl alcohol as the dispersant by 1 wt -.% Used.

509841/0 862

Method and apparatus for producing the two-layer film were as in Example 1, except that the first 16 cylinder ujas kept for drying at a temperature rising from 70 to 9O ⁰ C., the cylinder 17, a temperature of 115 ⁰ C. and had the temperature of the cylinder of the satinizing device was 175 ^° C.

The properties of the structure are listed in Table 1.

Example 2

A binary connected film made of the mixture of cellulose fibers mentioned in Example 1 and an aqueous dispersion of polypropylene fibers (isotacticity index = 93; melt index at 26O ⁰ C. = 10, melting point = 17O ⁰ C.) with a diameter between 15-35 / U, a length between 1-4 mm and a specific surface area of 7 m / g, the surface of which was coated like the polyethylene fibrils of Example 1, the concentration of the polypropylene fibers in the aqueous dispersion was 20 g / l.

Using two mounted in series Fort containers with curvy table, the second of which contained ^the first dia dispersion of PoIypropylenfibrila and the cellulose fiber dispersion, a film was prepared on a 30 m / min running conveyor belt, consisting of an underlayer of Polypropylenfibrile of about 1 mm thick and an overlying, about 2 mm thick layer of cellulose fibers.

This sheet was passed through 3 suction devices, where its water content was reduced to 75 % . Then she got over at a pressure

509341/0862

«Ρ

of 50 kg / cm * "working" wet "-Presses passed, and finally passed over 17 drying cylinders or rollers, one of which worked at a temperature between 60-130 C. first 16, 17, the mährend a temperature of 165 ⁰ C. After 4 rolls of the calendering device kept at 198 ° C. and exerting a pressure of 60 kg / cm, the connected FoIiB was cooled and wound onto a spool.

Example 4_

With the continuous device shown in Fig. 3, a "sandwich" structure was made, which consists of two outer Cellulose paper sheets and an inner film made of low density polyethylene.

For this purpose, two pulps with the following composition were used:
1) an aqueous mixture of cellulose fibers with a fiber concentration of 10 g / l and a kaolin content of 18 wt.

and 2 wt -% "Aquapel.";

2) an aqueous mixture containing 20 g / l low sinterized Polyäthylenfibrilen (melt index = 5; melting point = 115 ⁰ C.) mm with a diameter between 10-40 / U, a length of between 1.5-5, a specific surface area of 6 m / g, with 0.05 - were covered% of the dispersing agent used in example 1..

841/0862

The cellulose fiber mixture was over two mold containers with a curved Table while the polyethylene fibril mixture was fed to a flow box with a flat table.

The three-layer structure made of cellulose / polyethylene / cellulose was after passing through extractor and between "wet" -Preseen that a pressure v / on 50 kg / cm exerted dried by passing it through drying cylinder 7 of a rising temperature of 80-90 ⁰ C. until it had a moisture content of 0.1% by weight.

The melting of the intermediate layer of the Polyäthylenfibrile was then carried out by passing the film between the cylinders or rolls of a Satinier --- apparatus was passed were maintained at 15O ⁰ C. and exercised a pressure of 75 kg / cm.

After cooling, the structure was wound up on spools and stored. Its properties are shown in Table 1.

Example 5_

. According to a conventional manufacturing method with a device shown in Figure 1, a binary structure of a film of was mixed with 16 wt -.% Kaolin filled kraft paper and low density Polyäthylenkörnern a melt index of 8 prepared.

The paper film was first coated with a 0.2 wt .- ^ igen Solution of polyisocyanate in methylene chloride consisting adhesive impregnated, dried and then at one speed from 100 m / min to the head of a screw extruder, which was filled with polyethylene grains. There received the slide in the extrusion phase on its surface the semi-molten.

zenen polyethylene film. .

S09841 / 0862

The structure obtained in this way was passed between two cylinders, which exerted a pressure of 55 kg / cm; one cylinder was covered with rubber and the other was chrome-plated and was used for Cooling the polymer layer. The film was then collected on spools and stored. Their properties are shown in Table 1 "listed.

The following table shows the adhesion according to ASTM D 413/39 measured using a tensile speed of 10 cm / min. The permeability to water vapor was calculated as follows:

g χ 25 / rev

m ² χ 24 hrs

The permeability to oxygen and CO "became as follows

certainly:

ecm.cm.10

cm .see.cmHg

508 841/0862

characteristic

cn ο co co

Thickness of the structure; / U, thickness of the thermoplastic layer; <U

2 '

Weight; g / m

Tensile strength in Quenicht .; kg tensile strength in the longitudinal direction .; kg length at break in the longitudinal direction .; m length at break in transverse direction .; m tear strength in the longitudinal direction .; g tear strength in transverse direction .; g longitudinal brittleness; g.cm transverse brittleness; g.cm burst strength; kg / cm porosity; sec ^ liability; g / ccm permeability to water vapor permeability to oxygen permeability to CO ₂

Table 1 Example »2 • Example 3 Ex. 4 Example 5 1 ro
cn Example 1 76 80 95 81 co 85 19th 20th 15th 18th 20th 75 85 90 81 ¹ 80 4,? 2 6.12 5.33 5.12 4.48 3.48 3.67 3.17 2.98 3.20 4100 4500 3700 3950 3500 2900 2700 2200 2300 2500 55 50 32 35 45 60 70 42 45 58 4.9 4.5 3.5 3.5 4.5 3.0 3.0 2.2 2.0 2.8 1.7 1.8 1.4 1.5 1.5 0 0 0 0 0 10 10 10 10 10 4.1 • 7.5 12th 15th 5 0.1 0.2 0.4 0.5 0.1 0.3 0.5 1.5 1.6 0.4

Claims (5)

Claims T ^ l / experienced for the production of connected structures Cellulose paper sheets with films of thermoplastic polymarem material, characterized in that one (A) a film of at least two superimposed fibrous Forms strata, each strata at least predominantly from cellulose fibers bzuj. Fibrils or microfibers Thermoplastic synthetic polymer consists »by making diB pulps or aqueous dispersions of these fibers and Fibrils are stratified one after the other or in layers one on top of the other brings; (b) the water content of the film by means of suction and / or compression reduced to 30-80 wt .- / α; (d) the film to a moisture content below 0.5 wt dries; and (d) the film under pressure to a temperature above the softening temperature of the thermoplastic polymer is heated. 2.- Uerfahren according to claim 1, characterized in that one between steps (b) and (c) the film is cold compressed at pressures between 50-150 kg / cm. 3.- Uerfahren according to claim 1 and 2, characterized in that the fibrils of the thermoplastic polymer have a length between 0.5-5 mm and a diameter between 3-60 , u . 4. - Method according to claim 1 to 3, characterized in that the aqueous dispersion of thermoplastic polymer fibrils Has a fibril concentration that is 1.5 to 2.5 times the concentration the cellulose fibers in the corresponding aqueous 508841/0 8 82 - 19 dispersion is. 5.- The method according to claim 1 to 4, characterized in that that the thermoplastic polymer constituting the fibrils is polyethylene. 6, - Method according to claim 1 to 4, characterized in that the fibril forming thermoplastic polymer polypropylene is. 7 · - Method according to Claims 1 to 4, characterized in that the thermoplastic polymer constituting the fibrils is an ethylene / propylene copolymer with a predominant content of Is propylene. The patent attorney: S0SS41 / 0862 Blank page