DE2147321C3 - Thermoplastic, heat-sealable compound for the heat-sealable finishing of web-shaped fiber material and its use - Google Patents

Description

50

The invention relates to a thermoplastic, heat-sealable composition for the heat-sealable finishing of In water, paper-like, in particular unsized, web-like fiber material produced in water. One such For the sake of simplicity, fiber material is referred to as paper or paper material in the following, but this is not the case is not to be understood as paper in the narrower sense. The invention further relates to the use of such Masses for the production of paper material.

It is known that fibrous paper material for use as packaging material for infusion purposes in the manufacture of tea infusion bags and the like is suitable. For many years, a number of attempts have been made to use paper material of the type described above to impart heat-sealable properties, whereby a heat-sealing of the Infusion bag at its edges is possible while at the same time influencing or Can avoid deterioration of the infusion properties of the paper when used for tea bags or the like. It is necessary to have an effective seal Achieve that when immersed in hot or boiling water even for a considerably longer period Period is stable Originally, this was achieved by using a granulated or powdered, thermoplastic, heat-sealable composition on a surface of a previously formed, porous paper material spread and the granulated material was partially melted, causing it to adhere to the paper, without destroying its porous structure. The thermoplastic resin generally used was made made of a vinyl chloride-vinyl acetate copolymer, which is easily available in powdered form the resin is not available as a fine powder and not only led to an extraordinary result in the case of the paper rough surface texture, but also too unaesthetic, translucent, on the Paper scattered stains. When initially heating the copolymer for better adhesion of the resin on the fibrous paper structure also shrunk the resin, making it undesirable agglomerated or clumped. Furthermore, the molten resin tended to lower the liquid infusion rate by belittling the paper. Finally, problems arose in that the resin accumulated on the sealing machine's welding jaws. Although the copolymer also through discontinuous roller application or similar measures brought to the preformed paper materials treated in this way have never been particularly successful commercially.

In US-PS 24 14 833 a highly porous paper material made in water is described, to which the heat-sealable vinyl resin in fiber form is added The thermoplastic fibers are at least about 1.6 mm long and become mechanical with the cellulosic fibers during papermaking devoured. This allows a level of controlled tissue intermingling to be achieved that cannot be achieved with the powder used up to now. The heat-sealable fibers can be in the fabric are, however, preferably mainly distributed on a surface of the paper material arranged.

Although the copolymeric vinyl resins used in the paper materials are according to the corresponding After FDA guidelines were approved, tea inspectors could always find small traces of material that was in the hot or boiling water used to make tea is given off by the resin. As a result of these recognizable and taste-impairing properties, there was a search for improved ones Sealing methods and also after other thermoplastic materials for use as heat sealable Component in such paper materials.

In this regard, there have been some improvements compared to copolymer powder-coated Paper achieved by the copolymer through polyethylene and similar thermoplastic polyolefin powders has been replaced, which does not have the undesirable taste-impairing properties exhibited more. Because polyethylene has a specific gravity less than 1, it generally will onto preformed paper in powder form or as

uniform thin layer or film, which is subsequently destroyed by heat shrinkage, is applied. Unfortunately, paper treated with polyethylene powder in this manner exhibits many of the same disadvantages as they do also previously occurred with powder-coated materials. For example, the powder does not stay on stick to one side of the paper. In addition, it is difficult to make the powdered polyethylene suitable Way to melt it onto the paper without the appearance of degradation at the same time as a result of the action of heat occur in the paper material.

With the help of both methods described so far, i. H. With powder or films that are subsequently destroyed, it is not possible to use polyethylene in the paper to anchor oneself in the advantageous manner as in the known from US-PS 24 14 833 wet paper production is possible attempts to use polyethylene powder To supply wet parie to a paper machine, that is, in a manner similar to that in the aforementioned US patent described, encountered numerous difficulties, most notably the flotation of the material as a result of it low specific gravity.

The aim of the invention is to create a thermoplastic, heat-sealable composition of the type described at the outset Type of heat-sealable finishing of, in particular, suitable for infusion purposes paper-like fibrous web material without the disadvantages described above, but with the Advantages of the fibrous and powdery heat-sealable materials are retained. At the same time a improved sealing strength can be achieved with less need for heat-sealable material.

To solve this problem, the thermoplastic, heat-sealable composition according to the invention is thereby characterized in that the heat sealable material consists of composite, heterogeneous particles which in turn, at least 25-75% by weight and more of a thermoplastic, granulated polyolefin powder component contained in a refined carrier matrix made of a vinyl chloride-vinyl acetate copolymer, compared to the first incompatible or immiscible polyo'.efin resin finely divided and firmly embedded wherein the heterogeneous particles in water are not a self-supporting, water-separated web can form and at least 90% of the particles are smaller than 0.417 mm.

Heat-sealable, fibrous infusion paper material equipped with the heat-sealable composition according to the invention is suitable for use in tea infusion bags and the like. The sheet material shows improved Heat seal strength when in a wet papermaking process made of fibers for papermaking and fiberless, water-dispersible, composite, heat-sealable particles is formed. The particles are heterogeneous and cannot themselves Form a self-supporting web separated from water. The particles contain at least about 25 percent or more of a granulated polyolefin, which is in a very delicate, fibriline network made of a thermoplastic vinyl copolymer, is finely distributed and embedded. The composite particles are in the process of being formed by dynamic flow filling of the carrier resin from its solution in which the granulated Polyolefin is dispersed, refined and have an irregular shape.

A heat-sealable infusion paper material equipped with the composition according to the invention is particularly advantageous in that it contains heat-sealable particles which have the beneficial properties of powdery, have heat-sealable materials, but which are incorporated into the paper and retained in it can be. The paper material equipped in this way shows a uniform, heat-sealable surface which in particular no longer has a disadvantageous roughness or translucent spots, which is a disadvantage of paper material containing powdery vinyl copolymers is

Another advantage of a heat-sealable paper web material equipped with the composition according to the invention lies in an improved heat seal strength, a greater resistance to delamination in hot or boiling water as well as better taste properties, whereby one with smaller amounts of heat-sealable particles and no deterioration in the dry-seal properties occurs

A particularly advantageous property of the particles is that they are with the fibers of the paper material can be anchored and thereby form a firm, mechanical bond with them, while at the same time the Benefits of granulated, heat-sealable materials are retained.

The invention thus advantageously provides water-dispersible, composite, heat-sealable Particles with a very fine, thin, refined, irregular, kneady, chain-like appearance, which is particularly good for use as a heat sealable component of unsized, fibrous infusion paper material are suitable. A composite particle is used with particular advantage for this purpose from a solid dispersion of thermoplastic granules arranged in an irregular, network-like shape Arrangement of stretched, fine, fiber-free, but fibrillin-shaped strands of a vinyl chloride-vinyl acetate copolymer, which is preferably immiscible or inert with respect to the former and is finely divided are embedded.

A heterogeneous, composite particle according to the invention is also particularly advantageous, consisting of physically unchanged, granulated, heat-sealable material that is converted into a fibrous Paper material can be incorporated in the wet end of a paper machine. The paper matter! receives thereby heat-sealable properties and improved sealing strength, with granulated material from a fine lattice of thermoplastic carrier strands made of vinyl chloride-vinyl acetate copolymers locked in and held.

According to the invention, a composite, heat-sealable, granular component is particularly advantageous containing particle which can be introduced into a wet process for the production of paper. The particles according to the invention show no auto-adhesive properties at room temperature or below temperatures required for heat sealing. The particles continue to show no contraction or shrinkage properties when heated, avoiding agglomeration and the paper material in which the particles are embedded, at the same time a smooth surface receives.

The invention thus also relates to the use of the thermoplastic heat-sealable compositions for production of paper. The composed cells of the masses are mixed with the fibers and im Paper anchored, the particles themselves being none

can form self-supporting web separated from water and 90% of the particles are smaller than 0.417 mm and the particles consist of individual, granulated components that are distributed and embedded in a refined carrier resin matrix.

When a paper containing the particles for the manufacture of infusion packs, e.g. B. tea infusion bags o. The like. Is used, the thermoplastic heat-sealable compound has the advantage that the The accumulation of resin on the welding jaws is kept to a minimum or significantly reduced.

It is also particularly advantageous to achieve the advantages described above in a simple and simple manner economical, preferably using materials that are approved according to the relevant FDA guidelines. These advantages exist in particular that infusion paper materials equipped with the heat-sealable composition according to the invention have improved taste properties and a have more favorable appearance and excellent heat seal strengths, with approximately one third of the heat sealing material previously required is saved.

Further advantages of the invention emerge from the context or are described below.

The invention is described in more detail below with the aid of the figures on the basis of some preferred embodiments.

The pictures show:

F i g. 1 shows a flow diagram of the use of the compositions according to the invention in papermaking,

F i g. Figure 2 is an enlargement (38 times) of the composite, heat-sealable particles according to the invention;

F i g. Figure 3 is a further enlargement (60X) of heat sealable particles made by the method of the invention. The one in the carrier component embedded granulated component can be clearly seen in the figure.

In Fig. 1 is the use of the compositions according to the invention in papermaking in the form of a The flow sheet shows the stretched, refined, composite, heat-sealable particles two different thermoplastic materials according to the invention can be produced by means of a technique which simultaneous precipitation and elongation involves the composite particles becoming fluffier in shape Precipitates are formed and are characterized by the presence of stretched, non-granulated strands which anchors onto conventional papermaking fibers during the formation of the paper web The composite Particles are not bad. Fibers and can itself not a stable, unsized paper that is 100% made of the particle is made up of form. Correspondingly, the particles must be combined with other paper-making fibers can be combined to give the desired stable, fibrous paper structure.

When producing the mass according to the invention the carrier resin dissolved in a solvent suitable for this component and the insoluble, granulated resin component is then dispersed in the carrier resin solution en precipitant for the carrier resin is subjected to appropriate flow properties to achieve the desired refinement generate, for example, by moving quickly, stirring or other seer conditions or, in simple way, by flowing rapidly through a tubular precipitation chamber. The resin dispersion is added to the precipitating agent under these conditions. When the carrier resin is out of solution fails, it takes the one shown in FIG. 2 shown elongated, fibrillin-shaped structure that anchors the, contains undissolved, thermoplastic, granulated component. The granulated resin component is im Carrier resin embedded and enclosed and in the matrix of the elongated, fibrous precipitate held. The granules are physically during

ίο not changed during the entire precipitation step but firmly anchored in the carrier resin. The actual appearance of the heat sealable particles is given on best from Fig. 3. As you can see, are everywhere in the Carrier resin matrix discrete granules of undissolved Resin spaced at random. As can also be seen from Fig. 3, this is the case Carrier resin does not exist in the form of strands of the same shape and size. The carrier matrix fluctuates in On the contrary, largely in terms of their shape and size and appears to be made up of a wide variety of fibrillin-like To consist of strands extending in and out of the main structure at random. As a result of the random dispersion of the granulated component, some strands of carrier resin embed this granulated thermoplastic resin, while others are completely free of any granulated particles are. This fibrillin structure, which is largely subject to the laws of chance, has the consequence that the heat-sealable particles extremely well rend of papermaking to be held, though more than 20% of the particles have a largest diameter of less than 0.4 mm and not even in the Are capable of forming a stable, unsized paper in the absence of other papermaking fibers. the Particles can be easily dispersed in water and in the wet end of a paper machine are fed in much the same way as conventional fibers for papermaking. Preferably However, the particles are supplied so that a two-layer, heat-sealable infusion paper material. It can be assumed that the Particles from their aqueous dispersion medium are filtered through the initial deposition of papermaking fibers before being complete Paper material has formed or the paper is completely drained. The particles are preferably in the Arranged near a surface of the paper and thus give it the desired heat sealing properties. It is of particular advantage that the

thus heat-sealable particles according to the invention have particularly favorable properties. They show Wat em al rar »te α nrai + cvelianst train α QnhntTnnFiinir l ^ oirrt

Heating in the conventional paper drying system, little or no tendency to agglomeration or auto-adhesion as well as resistance to adverse penetration of the paper material at heat sealing temperatures. The granulated resin component makes about a quarter and more, preferably about half the total weight of the particles.

The properties of the granulated, thermoplastic Materials are clearly noticeable in the finished paper material during heat sealing.

The normally solid, synthetic, thermoplastic resins used as raw material are not only different in terms of theirs

Composition, but also show in general

'Must have a degree of intolerance in particular the thermal used as the granular component

plastic material of the composite particles must be insoluble in a solution of the carrier resin. Different said the solvent must be able to dissolve the carrier resin, but the granulated resin relatively unaffected, d. H. remains unsolved. The carrier resin component must also be easily precipitated from the solvent under the necessary conditions so that the desired Refinement of the particles is obtained.

The vinyl copolymer carrier resin used is made from a copolymer of vinyl acetate and vinyl chloride. The thermoplastic vinyl copolymer is readily soluble in acetone and can be extracted from its solution by adding to a suitable precipitating agent, z. B. water or water-acetone, are easily precipitated. The particular polymers used are Approved according to the relevant FDA guidelines. In particular, polymers are used with respect to their heat sealing properties are suitable. In general, solid, fully synthetic, fiber-forming, thermoplastic resins used as far as they are pairs or groups form which the formation of the desired composite, granular-fibrous structure of the obtained Allow heat sealable particles. Therefore, other resins may also be used depending on their respective Re-use can be used, e.g. B. polyolefin compositions including polyethylene, polypropylene as well as the copolymer e.

For a more detailed explanation, the invention is explained below with reference to the corresponding FDA guidelines for use in tea infusion bags or the like approved vinyl copolymers are explained. Accordingly, a preferred granulated resin component is made of a polyolefin composition of the polyethylene type and the carrier resin consists of a copolymer composed of about 86% vinyl chloride and 14% vinyl acetate. It should be emphasized that a special form of the as the starting material The carrier resin used is insignificant because the carrier resin is dissolved in the formation of the masses.

It should also be emphasized that the particular solvents and precipitating agents used can vary depending on the particular resins used. In the preferred embodiment of the invention, the solvent used consists of acetone, not only because of its solubility properties, but also because of its adaptability to the precipitation process, whereby the carrier resin can be precipitated simply by adding it to water or a water-acetone mixture.
The granulated resin component remains unchanged during the particle-forming precipitation process. The size, configuration and properties of the granulated resin component can thus be selected according to the hamlet use of the end product. It consists of a fine powder of a thermoplastic, synthetic polyolefin, a larger part of the granules having a particle size which is essentially smaller than 75 μ. At least 40% of the material should fit through a sieve with a mesh size of 0.044 mm. The size distribution of the particles varies between approximately 10 μ and approximately 100 μ, the material preferably used being in the lower half of this range. One material of the type described above which has been used with good results is a commercially available polyolefin powder, which is believed to be an ethylene-butylene copolymer. The material shows a specific density of 0.96 to 23 ° C (ASTM D-1505-63T), a melt index of 12.0 (ASTM D-1238-62T) and a softening temperature of 126.7 ° C (ASTM D- 1525-58T). The shape of the material is relatively uniformly spherical to spheroidal.

"The material shows a non-linear or arbitrary one Molecular chain orientation. At least 85% of the PuI

jo vers fit through a sieve with a mesh size of 0.15 mm, more than 80% through a sieve a clear mesh size of 0.074 mm and more than 40% through a sieve with a clear mesh size of 0.044 mm. The ratio of granulated component to carrier resin component can vary considerably, although a ratio is generally preferred, the amount of the granulated component being more as 20% by weight of the composite heat-sealable particles obtained, especially when the particles for making heat sealable infusion paper materials for use with Tea infusion bags and the like are to be used. In Table I is the effect on heat seal properties of the obtained infusion paper depending on various proportions of granulated component reproduced for carrier resin component.

Table I.

Properties of a! Rifusic paper *) with different particle compositions

test

Polyethylene: vinyl copolymer ratio : 70 20: 80 25: 75

55:45

65
260

Damping (sec.)
Dry delamination (g / in)

*) Two-layer paper. All paper stocks contain about 30% by weight of heat sealing particles.

210
305

600+ 260

600+

As can be seen from Table I, there is a noticeable increase in the heat sealing properties of the infusion tube 65 without adversely affecting other properties of the paper stock.

Certain upper limits on the proportion of granulated resin component in the assembled, heat-sealable particles can also be drawn.

piers on when the concentration of granulated Component increases from 20% to 25% and above These improved properties are obtained

be genes. In wet paper making processes, heat sealable particles are smaller in specificity Density than 1.0 undesirable. Accordingly, the upper limit for the granular component is approximately 85% when a polyethylene powder having a density of 0.96 is used as the granular component of the particles is, and the vinyl copolymer carrier resin a Has a density of about 1.36. Above this percentage, the composite, heat-sealable Particles have a specific gravity that is close to or less than 1.0. The particles tend then, accordingly, for swimming on the surface. In reality, in practice one will maximum proportion of approximately 70-75% used. The maximum proportion is also preferable because the physical uniformity of the heat sealable particles between 70-75% and 85% is very poor and can very easily be destroyed even with the low degree of movement experienced during the Papermaking occurs The destruction of the heat-sealable particles leads to a breakout of im substantial free polyethylene granules, causing flotation and foam stabilization problems in the Paper machine surrender. In addition, the high percentage of granulated component during the • Drying causes poor adhesion to the conventional fibers of the infusion paper, which an infusion paper material is produced that has a low dry seal strength.

At the same time it must be pointed out that the economy of the precipitation process for one large proportion of granular component speaks because as a result, higher hot-seal particle-to-solvent ratios at primary dispersion and higher output rates can be achieved. Larger proportions of granulated component additionally lead to smaller amounts of self-adhesion during removal the precipitation of heat-sealable. Particles and advantageously to a smaller particle size obtained heat-sealable particles.

On the other hand, small proportions of the granular component have advantages in papermaking. Namely, heat-sealable particles with greater stability during papermaking, which are easily dispersible so that little or no trouble arises due to floating material, are obtained. However, as can be seen from the results summarized in Table I values results in a deterioration of the heat-seal strength of heat-sealable particles, when the content of granulated component is less than 25% The binder obtained also tends below this limit for self-adhesion, and has a coarser or larger fibrous structure , as a result of which the limits of the desired particle size described below are substantially exceeded. The optimal ratio of granulated to carrier resin components is between 1: 3 and 3: 1. Within this ratio, a system is obtained that combines the advantages of both the production of the heat-sealable particles and the wet process for papermaking. It goes without saying that the exact proportions of the components can vary, depending on the particular starting materials used the economy of the precipitation process used in each case, the paper manufacturing systems using the heat-sealable particles and the requirements that are placed on the infusion paper to be manufactured. However, the above conditions have been found to be the most suitable for the production of infusion type paper materials for tea infusion bags and the like.

The composite, heat sealable particles of the invention are made by the thermoplastic dispersion to form a precipitating agent for the carrier resin under suitable agitation conditions is admitted. In the precipitation process will

ι ο the dissolved, synthetic, polymeric material at the same time subjected to severe shear conditions with the precipitation. This creates a tearing apart and Stretching of the precipitation causes refined, heterogeneously composed precipitation particles. The dispersed, granulated components remain physically unchanged in the carrier solution is firmly embedded or planted in the carrier resin during the refined precipitation, whereby its granular properties are retained. Although the technique of simultaneous shear precipitation is similar to a process used in the cellulose acetate industry and in the manufacture of fiber-like Materials (fibrids) are used, the composite, heat-sealable particles are detected of the invention does not have certain essential properties of a fiber-like material. the Particles according to the invention in particular neither form a paper structure, with intact wet strength, nor are they actually fibrous in shape.

You are not able to form a stable, unsized paper on your own. More precisely, can Paper webs that consist only of these particles are not removed from a paper web-forming wire and show little or no stability after drying in air.

It goes without saying that the nature and severity of the movement during the precipitation of the heat sealable Particles can be varied because the formation of a fiber-like structure is not required The refining forces must, however, be great enough to give the precipitating resin a stretched, to impart fibrillar shape or property, making them in a process for the manufacture of Paper can be used and anchored in the paper material by conventional paper fibers.

It is believed that the absence of any shrinkage of the composite particles upon heating is due to the unoriented character of the carrier resin which forms during the precipitation process

The concentration of the carrier resin in its solution before precipitation can be varied within certain limits. However, it is generally kept below 35% by weight. The actual useful working range is about 10-30% by weight, with the preferred range for the

Vinyl copolymer in acetone at about 17-20 wt%

cherishes

To get the best results are

certain temperature and concentration conditions of the precipitation solution are required. If that Carrier resin is dissolved in an acetone solution A precipitant containing a mixture of acetone and water can be used, provided that the Precipitation solution consists of less than about 50% acetone and has a temperature below that Room temperature, d. H. below about 25 ° C, will eme, or both of these, are interrelated

conditions vary, the resulting composite particle is affected. One For example, acetone concentrations in the precipitation solution of less than about 25% will lead to poor economic results in the isolation system. The preferred working concentration for the precipitation liquid is therefore between 25 and 50% Acetone, with a typical concentration being around 38%

As already stated, temperatures of more than 25 ° C. are undesirable Worked at a temperature of 30 ° C, then the particles acquire adhesive properties, tend to agglomeration and form particles of an undesirable size, especially when working on granulate components at low concentrations. The temperature of the precipitating agent is preferably in the range between 0 and 5 ° C. These temperatures cause a good dispersion of the precipitate and facilitate filtration of the resulting composite particles. The preferred precipitating agent used accordingly consists of about 38% acetone and is kept at a temperature of about 0 ° C. Under these conditions, the composite heat-sealable particles remain dispersed and show no undesirable self-adhesion.

As mentioned above, the size of the composite heat sealable particles will depend on numerous factors. The particle size should in general for the papermaking process and for the ability of the paper machines to work with dispersions of the particles may be appropriate.

In general, large particles provide poor dispersions in the papermaking system and exhibit poor weight poor entangling and adhesive properties on the paper fibers during the conventional paper drying process. Large, coarse particles result in addition, a relatively rough surface, tend to flatten out (coming effect) during processing and lead to disadvantageous, translucent stains in the sealing area of the infusion paper. Small Particles, of course, make good dispersions during the papermaking process and have excellent felting and adhesive properties the paper during the drying process. The particle size increases with increasing shear forces during the precipitation. The shear force can increase of course with the speed of movement of the Change the precipitant and its viscosity. The period during which precipitation is high is plastic and deformable, affects the size of the resulting heat-sealable particles. By extension Reduction of the precipitation time, for example when using When a precipitant containing large amounts of the polymer solvent is formed, the shear forces will have more opportunities to destroy the structure, thereby creating a heat-sealable particle with less Greatness arises. Very small particles, for example on the order of polyethylene powder, are undesirable because they are contrary to the purpose of the invention. Appropriately, the particles are after Bauer-McNett scale classified The separation is on made of an aqueous particle dispersion and is given in percent by weight that with sieves different size is obtained. In general, particles are passed through a sieve with a clear Mesh size of 1 ,! 7 mm withheld for use in the manufacture of heat sealable Infusion paper materials undesirable for the reasons described above, a proportion of about However, 1% of the particles are portable. Particles produced by

jo a sieve with a mesh size of 0.42 mm withheld are also disadvantageous, but to a lesser extent; up to 10-15% are acceptable. The precipitation conditions must accordingly be chosen so that there are essentially no particles arise which are larger than 1.17 mm, and that at most about 10% particles larger than 0.42 mm arise. For the remaining 90% of the particles, a normal size distribution is preferred, with the average size distribution about that of a sieve with corresponds to a mesh size of 0.10 mm. A Pair of examples with heat sealable particle size distributions which are excellent Results are shown in Table II.

Table II Size distribution *) of the composite particles Sieve Mesh Sieve Size (mm) Retained

Particle (%)

150

Pan

1.17 0.42 0.10

*) Bauer-McNett scale.

0.2

M. 35.8 62.7

0.3 10.7 56.2 35.8

It goes without saying that the particle size obtained in the shear precipitation using in the paper industry usual grinding devices is reduced, for example by the Pulp separator to Jordan. In fact, the strong hydraulic shear forces turn out to be as shown in a machine of this type are advantageous

compared to metal-on-metal-Berühning, as it is in other common Vermahhmgsvorrichtungen, for example in Dutch occurs

Table III gives in this connection the influence of the particle size on the properties of the under Using these materials manufactured, heat-sealable InfusionDaDiers again.

13 14

Table III Influence of the size of the sealable particles on the properties of the infusion paper *) Particle size

Retained by sieve by 0.50 mm sieve going with a clear mesh size and width of 0.42 mm held back by sieve with

0.10 mm clear mesh size

Steam resistance (set) 400 600+ Dry delamination (g) 210 210 Seal penetration (in-g / in ² )! 95 2

*) The sealable particles consist of polyethylene-vinyl copolymer in a weight ratio of 55:45. Classification according to the Bauer-McNett scale. Two-ply papers were made using paper with a nominal basis weight of 4.54 kg, from which about 1.36 kg sealing particles passed, produced

As can be seen from Table UI, the particles larger than 0.42 mm do not show as good heat sealing properties as particles smaller than 0.42 mm, but are larger than 0.10 mm. The results for seal penetration are particularly important. With these Tests mean large values that the thermoplastic, sealable resin has the fibrous paper structure in highly penetrated Penetration of this type causes resin to accumulate on the Heat seal baking of a sealing machine. It follows that a large percentage of particles larger than 0.42 mm is undesirable. This effect is even more noticeable with material, its Particles larger than 1.17 mm.

Although the lower limit of the particle size can be varied, it should nevertheless be noted that the particles must be large enough that they can be retained by the fibrous base during manufacture of the infusion paper. The above specified particle sizes relate to the manufacture of infusion paper for use in Coffee and tea products. However, there are other areas of application where the presence of larger Particle does not adversely affect.

For a better assessment of the shape of the heterogeneously composed particles, refer to Fig. 2 and F i g. 3, in which typical particles according to the invention are depicted. In Fig.2 is the refined, fibrillin-like property of the flaky precipitate clearly recognizable. F i g. 3 shows against it the chain-like, knotty strands that are characteristic of the composite particles. the The shapes of individual particles change considerably and randomly; their elongated, non-granular character is also clearly recognizable. The composite, heat-sealable particles will after precipitation usually filtered and washed thoroughly before being redispersed in water for further use in the wet end of a paper machine.

When using the composition according to the invention for the production of heat-sealable infusion paper material, a dilute dispersion of heat-sealable Fibers made of a vinyl copolymer and with a length of at least 13 mm to an entry of not thermoplastic fibers for papermaking when the fibers are on the papermaking wire be deposited. The vinyl copolymer fibers are preferably placed in the feed hopper Given paper machine. You will then be on the paper-shaped sieve along a central point the course of the sieve for fiber collection deposited.

When using the mass according to the invention is to achieve the same and even improved Heat sealers cut paper stock significantly less thermoplastic material is required. the Heat-sealing properties that were previously achievable with a certain amount of material can now also be achieved then achieve if only two-thirds of what was previously

H) required heat seal composition can be used. For example, if an infusion paper is made with a content of about 3.175 kg per ream (480 sheets, 60.96 χ 91.44 cm) of non-thermoplastic fibers, only about 031 kg per ream is on composite, heat-sealable particles required in order to achieve sealing properties for the heretofore 1.36 kg of vinyl copolymer fibers are required per ream became.

In view of the fact that the composition

The mixture of heat-sealable particles in the absence of papermaking fibers is not a stable, unsized one Can form paper, the use of the two-layer structure is generally preferable. However, it is also possible to use the particles with the fibers Mix completely and the papermaking Then use the mixture provided that the particles are sufficiently retained in the paper structure and not out of it during papermaking be washed out. If the composition of heat sealable particles and papermaking fibers is thoroughly mixed, it is desirable to have the thermoplastic particle composition firmly in the paper with finely ground cellulosic fibers to tie. Other conventional binders can can also be used successfully.

The infusion paper material obtained using the compositions according to the invention has has a thin, porous and light structure, but is of sufficient stability to withstand the Manufacture of tea infusion bags and the like required Procedural measures not to be destroyed. Paper materials of the type described above generally have a basis weight of about 4.08 to 7.26 kg per ream and are in the heat seals easy to work with the packaging machines.

The invention is explained below with reference to exemplary embodiments Quantities relate to weight.

Example I.

A carrier resin solution is prepared by adding 45 parts by weight of a vinyl copolymer resin (14% Vinyl acetate and 86% vinyl chloride), to be dissolved in acetone. About 55 parts by weight are added to the solution Polyethylene powder with a specific density of 0.96 was added. The obtained dispersion was mixed to obtain a dispersion of the polyethylene powder in the carrier resin solution. The solution was held at a temperature of about 29 ° C.

A precipitating solution was made from approximately 38% acetone and 62% water and cooled to 0 ° C.

The solutions described above are converted into a precipitation pipe with constant flow composite heat-sealing particles consisting of approximately 55% polyethylene and 45% vinyl copolymer, manufactured. The precipitation solution is passed through a central, tubular part at a speed of about 5.5 g / min and the resin suspension is fed at a rate of 0.4 g / min to the flowing precipitant solution through a hole located on the side of the tube. The so The composite fibrous particles obtained are filtered, washed with water and dried Re-dispersed for further use in the papermaking process.

The dispersion of heat-sealing particles is passed through a pulp separator to Jordan and brought into the feed hopper of a paper machine, the feed speed is sufficient to allow a to give finished paper with a 20 wt .-% proportion of heat-sealing particles. The resulting Infusion paper material is excellent in appearance, has good heat and wet seal strength on, is tasteless and in all other properties with conventional, heat-sealable ir.fusion paper materials comparable. The paper obtained is used for further processing into tea infusion bags used on the usual form and seal machines. The tea infusion bags produced in this way have excellent hot and wet sealing properties.

Example II

The process according to Example I is repeated, with a polypropylene powder in place of this polyethylene powder is used. The heat-sealable particles obtained are used to produce a two-layer. heat-sealable infusion paper with a total concentration of thermoplastic particles of about 30% of the total paper weight used. The resulting paper has, like the paper material in Example !, excellent properties.

For this purpose 2 sheets of drawings

Claims (4)

Patent claims: 1. Thermoplastic, heat-sealable mass for the heat-sealable finishing of paper-like in water produced, web-shaped fiber material, characterized in that the heat-sealable Material consists of composite, heterogeneous particles, which in turn at least Contain 25-75% by weight and more of a thermoplastic, granulated polyolefin powder component, those in a refined carrier matrix made of a vinyl chloride-vinyl acetate copolymer the first incompatible or immiscible polyolefin resin is finely divided and firmly embedded, wherein the heterogeneous particles do not form a self-supporting water-settled web in water and at least 90% of the particles are smaller than 0.417 mm. 2. Composition according to claim 1, characterized in that the granulate component is a polyolefinpu! - ver includes a specific gravity less than 1.0, a melt index of about 12.0 and a has a largely uniform, spherical structure, and a particle size distribution, according to that more than 80% of the particles are smaller than 0.074 mm and more than 40% smaller than 0.044 mm. 3. Composition according to claim 1, characterized in that the composite particles a have an average size of about 100 μ and about 55% by weight of thermoplastic polyolefin granules made of polyethylene or polypropylene polymers or copolymers with a specific Density less than 1.0 and about 45% by weight stretched vinyl copolymer in a more refined, fibrillar shape Contains arrangement, wherein the vinyl copolymer, the polyolefin granules in a chain connects and holds on. 4. Use of compositions according to one of claims 1 to 3 for the production of paper, characterized in that the composite particles are mixed with the fibers and in the paper are anchored, the particles themselves not forming a self-supporting, water-separated web and 90% of the particles are smaller than 0.417 mm, and the particles are individual, granulated Components that are distributed and embedded in a refined carrier resin matrix.