CS203266B1 - Method of manufacturing packing material - Google Patents

Description

The invention relates to a process for the production of packaging material, predominantly of cellulose fibers, which exhibits only a slight change in length after water absorption, can be welded by radio frequency and has a low tendency to block. The material can be used to create linings in vehicle construction.

It is known that cellulose has the property of absorbing or releasing moisture from the ambient air. This leads to swelling or swelling of the fibers, which leads to much unpleasant dimensional changes in the overall fiber web. In the range of up to 100% relative humidity, this property is generally referred to as dimensional stability. The water is deposited on the cellulose mainly by chemisorption. Technical measurement measures dimensional stability most often as a length change between two relative air humidity, for example between 35 and 85%. It represents the measure of expected shape changes under normal climatic conditions.

The ratios are substantially different when the fibrous web comes into contact with liquid water. During the additional adsorption processes on the micelle surface and capillary condensation in intermicellar spaces, water is stored until saturation. This results in a much stronger swelling, which can even lead to the breakage of the fiber web.

Attempts have been made to prevent water from entering the fiber web or to prevent the absorption of moisture from the air. In paper industry, the usual sizing of rosin does not help in any way. Therefore, the fibrous webs are impregnated either in the mass or on the surface by other auxiliaries such as bitumen or paraffins, dispersions based on polyvinyl acetates, polyacrylates, polyvinyl chlorides. For special purposes, it is also common to apply silicone compounds to the surface. Finally, it is also known to add inorganic or organic fibers prior to the production of the sheets, which themselves are unable to absorb any water or only a small amount of water. A good example of this is the addition of glass fibers. In practice, there are also methods in which films such as polyethylene films are applied to the cellulosic fibrous web by laminating or tempering. Finally, the still wet fiber web is dried under pressure in a heated press.

The addition of excipients prior to the production of the leaves is not very effective for the aforementioned purpose of use, large amounts of the additive and the improvements achieved are required. Porovnatsl20326B me. rQal4 _{f #} K-rorně that appear most frequent · _(IZT £ §pjié tiproblétny wastewater, ne'b;Qi'ř these additives are only unsatisfactorily retained in the fibrous web.,

Surface impregnations with bltumen, paraffins or other waxes have the drawback that they cannot be welded by high frequency welding. One of the two layers for this suitable material acts against its repulsive character against aqueous liquids. The solvent-containing layers are undesirable in view of the increased cost and the associated handling problems.

Aqueous dispersions such as polyvinyl chlorides, polyvinyl acetates, polyacrylates and / or polyvinyl acetates ^. although their copolymers are capable of high frequency welding, they do not protect sufficiently against dripping water and exhibit too low block strengths. An example of this is polyvinylidene chloride, whose copolymers, while impregnating, improve the dimensional stability of the fibrous web compared to the different relative air humidity, but exhibit too great a change in storage over a prolonged period of time and only provide intermediate block strength.

The addition of non-cellulosic fibers, such as glass fibers, fails to result in reduced strength and absorbency. Silicone compounds cannot be radio frequency welded and are relatively expensive. The latter also applies to laminated films which have the additional disadvantage that the edges of the sheet material are not protected against water or moisture,

By pressing the moist fiber web at high pressure and high temperature in a heated press, length changes can be achieved after water absorption, which are close to those obtained by the method according to the invention, but this material absorbs too much water because of high drying temperatures. all auxiliary means become ineffective. In addition, this process does not present an economically advantageous solution due to the long drying times. ·

It is an object of the present invention to provide, in a suitable manner, a cellulosic fiber packaging material which overcomes said non-cetacies and is comparatively inexpensive.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a packaging material which, even after prolonged exposure to liquid water, absorbs only a small amount of water, in addition to being capable of high-frequency welding and forming a good flat film. The mechanical strengths must not suffer any losses and the packaging material must be low cost.

The essence of the process for the production of the packaging material according to the invention is characterized in that the woodboard containing at least 60% wood fibers is dried to a dry matter content of 96 to 98%, for example by infrared rays, with a degree of grinding of 25 to 45 ° SR. in linear hydrocarbons having a melting point of up to 80 ° C at temperatures corresponding to at least twice the melting point and then further impregnating with an aqueous dispersion consisting of a 60:40 vinyl chloride / vinylidene chloride copolymer containing 0.1 to 6.5 % of a modified triazinone compound, for example, dimethyloloxyethyltriazinone or 0.1-5.5% of a mixture consisting of monomethylurea and dimethylurea with at least 12% dimethylurea and finally carried out for 1 to 100 s by infrared heat shock drying at 120 to 140 ° C ,

The process for producing the packaging materials according to the invention permits subsequent coating with aqueous dispersions, without disturbing the film-forming nature of the alkanes. The absorption of the impregnating agent can be arbitrarily controlled. Suitable aqueous dispersions are dispersions based on polyvinyl acetates, acrylic acid derivatives, polyvinyl chlorides and others.

Packaging materials up to 5 mm thick can advantageously be produced by the method according to the invention. The effect can be enhanced by exposing the impregnated material to an infrared temperature shock of 120 to 140 ° C.

Larger amounts of additives of the triazinone compounds or of a methylolurea mixture again increase the length changes after storage in water and thus reduce the consumption value.

The advantage of the packaging material produced according to the invention is that it absorbs extremely little water up to 48 hours, with very little change in length, excellent surface placement even under the influence of different humidity and temperatures. In addition, the material can be welded by RF, has good block strength and a relatively low cost compared to comparable material.

The advantages of the process according to the invention are to be explained in several exemplary embodiments.

The blend, the old paper, is formed into a 3 mm thick fibrous web on a round sieve machine by pressing several wet layers. The grinding degree was 45 ° SR. The values are given in Table 1, Experiment 1. The same material is soaked in a manner known per se in paraffin with a melting point of 61 ° C for 20 seconds. The bath temperature was 95 ° C. The values are contained in Experiment 2. Experiment 3 comprises the values of the material produced according to the invention. The fiber web was soaked for 20 seconds in the same paraffin, but at 125 ° C and after drying to 96.8%.

ΤΌ32Β6

WITH

Taboo

1 (%) % s experiment 1 1.46 43.9 experiment 2 0.84 25.6 pokus 3 0.55 19.0 Length change. 1 represents average

longitudinal and transverse directions and were measured as well as the increase in thickness As and the increase in water uptake AG after 24 hours of uptake on 100 X 100 mm samples. Experiment 3 shows, as opposed to poT and bu

Experiment 4 water uptake (% J

.. 1.64 s 33.9

G 43,7 Moisture absorption (% j

0.23 with 4.00

G 2.03 radius of curvature (mm) longitudinal 265 transverse 101 block strength 4 Cobb / Unger water absorption (g / m ² ) after 5 minutes 20.85 after 30 minutes 87.75 after 60 minutes 113.55

To Table 2

Water uptake measurement was performed as in Table 1. Additionally, Cobb / Unger water uptake was only determined on one side of the packaging material. Moisture absorption was measured between different climatic conditions of 20 ° C / / 35% rel. humidity up to 20 ° C / 95% rel. humidity. The radius of curvature is a measure for the placement of specimen layers at 4 ° C / 95% rel. humidity up to 40 ° C / 10% rel. humidity. The block freedom was measured at 5 kp / cm ² and 40 ° C for two hours. The values represent a sequence of order, with 4 subdivisions in the cooled state without surface damage and 2 average surface damage. For Experiment 4, a board consisting of at least 80% wood fibers with a grinding degree of 52 ⁼ SR and a thickness of 2.9 mm was processed. The experiment was performed on a round sieve cardboard machine. The material was soaked in a vinyl chloride / vinylidene-chloride copolymer dispersion without the additive according to the invention and dried by convection drying. The absorption of the impregnating agent was 10.3%. For experiment 5, a cardboard containing 90% of the wood fibers with sludge was produced on the same machine

G (%) note

41.4 high frequency welding is not possible

21.9 high frequency welding, no deposition

2.5 can not be high frequency welding, but can be applied to piece 2 to improve the length change by about 62%. The thickness swelling and water absorption are also smaller. In contrast to Test 2, the material produced according to Test 3 could be overlaid with any aqueous dispersions without difficulty.

ka 2

6 7

0.69 36.2 51.3 0.34 21.0 26.7 0.22 12.4 22.8 _ 0.22 0.19 - 2.37 1.84 - 1.49 1.38 4470 4υζ J - 635 695 4 2 2 17.0 2.8 32.4 - 5.4 59.0 - 11.2 grinding degree 30 ° SR, and after previous su- here on 98.0% impregnated with the same conditions Attempt 4. Pro pokus 6 was the same cardboard as in the experiment

soaked after drying to 96.8% dry for 20 seconds, in paraffin with a melting point of 55 ° C at a bath temperature of 120 ° C, and then soaked in a 65:35 vinyl chloride / vinylidene chloride copolymer dispersion containing 5% methylolurea according to the invention . The paraffin content was

5.6%, the dispersion absorbed 4.1%. Convection drying was carried out at 60 ° C. The same conditions were chosen for Experiment 7 as for Experiment 6. Only the dispersion was applied by roller. The material contained 5.2% paraffin and 1.8% of the dispersion according to the invention. Drying was performed by IR temperature shock.

It can be seen from Table 2 that no significant improvements were achieved with respect to moisture absorption or dimensional stability. For length changes, on the other hand, an improvement of 83 ° / o can be seen. Emphasis may be placed on the results of Experiments 6 and 7 which, with substantially less absorption of the impregnating agent, give better results. The same applies to the reduction of thickness swelling and water absorption. Also flat placement2 (Γ32 Β 6 layer setting is better as it results from increasing the radius of curvature.

The behavior of the material according to Experiments 4 and 6 as a function of time results from the diagrams in which in FIG. 1 the time in hours is plotted on the x-axis and the longitudinal extension in ° / o in the y-axis. In FIG. 2, the time in hours is plotted on the x-axis, and the lengthwise elongation in% in the y-axis is plotted. Fig. 3 shows the time in hours again on the x-axis and the thickness change in% on the y-axis; and Fig. 4, where the time in hours again on the x-axis is the weight change in ° / o. In all of these drawings, 1 indicates experiment 6 and 2 indicates experiment 4 (i.e., the solid line corresponds to experiment 4 and the dashed experiment 6).

The exemplary embodiments clearly show the advantages of the material produced by the method of the invention. The preferred sector for use is vehicle construction, but it is also possible to use it in other areas, such as the construction industry.

Claims (1)

SUBJECT Process for producing packaging material, characterized in that the woodboard containing at least 60% wood fibers with a degree of grinding of 25 to 45 ° SR is dried to a dry matter of 96 to 98% and then immediately impregnated in linear hydrocarbons with a melting point of up to 80 ° C at temperatures corresponding to at least double the melting point and then further impregnating with an aqueous dispersion consisting of copolymers SUMMARY OF THE INVENTION A vinyl chloride / vinylidene chloride ratio of 60:40 containing 0.1 to 6.5% of a modified triazine compound, e.g. finally, it is carried out for 1 to 100 s with an infrared heat shock drying at 120 to 140 ° C.