HUP1000231A2 - Low cross-linked polymer film process for production thereof and use thereof - Google Patents

Description

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RARE SPACE NET POLYMER FILM, PROCESS FOR PRODUCTION AND APPLICATION

The invention relates to a rare crosslinked polymer film which is water-soluble and completely biodegradable in nature. The invention also relates to a method for producing the film and to the use of the film.

Background of the invention

Nowadays, when an almost unmanageable amount of plastic packaging is generated, and at the same time environmental considerations are becoming increasingly important, the use of water-soluble, naturally microbiologically degradable plastics is of great importance.

The most important raw material for water-soluble plastic films is polyvinyl alcohol. Several patents deal with polymer films made from polyvinyl alcohol, for example, US Patent No. 7,511,093 describes a film made from polyvinyl alcohol and a plasticizer. A polyvinyl alcohol film is also described in US Patent No. 7,517,478, where the hardness of the film is determined. A fast-dissolving polymer film is described in USP Patent No. 7,547,737, where the polymer comprises polyvinyl alcohol and a diacid. USP Patent No. 7,495,044 describes a biodegradable polymer comprising a modified starch, optionally a starch, a water-soluble polymer comprising, inter alia, polyvinyl acetate or polyvinyl alcohol, and further comprising a fatty acid or salt, optionally a plasticizer and optionally water. The produced polymer can be used for food packaging in the form of rigid or flexible film.

International patent application WO 2005AU16O5A describes a film-forming air barrier polymer comprising an optionally modified starch, a water-soluble polymer which may be polyvinyl alcohol, and further comprising sorbitol, a plasticizer, a fatty acid or its salt and an emulsifier system. The film made of the polymer is used as a backing layer in conjunction with conventional packaging materials. International patent application WO 2008/063468 describes the preparation of a water-soluble polymer suitable for dispensing detergents from polyvinyl alcohol, chitosan, alkali metal or ammonium bisulfite or metabisulfite, crosslinking agent and optionally plasticizer.

Chinese patent application CN 2007 10056353 A describes a biodegradable liquid mulch film, which is prepared from polyvinyl alcohol, carboxymethyl cellulose, starch powder, surfactant, plasticizer and crosslinking agent, diluted with water and sprayed onto the soil.

However, the dissolution time of polymers produced by known solutions is not controlled.

The aim of the invention is to produce a plastic film that decomposes in nature within a certain time. This would allow us to specifically deliver various substances, such as water treatment agents or nutrients for aquatic organisms, to natural and artificial waters. A further aim of the invention is to produce a polymer film that, when decomposed, can itself serve as a nutrient.

The rare crosslinked polymer film of the invention achieves these objectives.

106763-11255-BÉ-fa

-2Description of the invention

The film according to the invention is prepared from polyvinyl alcohol, vegetable starch and water with the addition of a plasticizer and a crosslinking agent. By varying the amount of the crosslinking agent, the dissolution rate of the produced film can be controlled within predetermined limits.

The film is produced in extremely simple steps: an aqueous starch solution is mixed with an aqueous polyvinyl alcohol solution, then a plasticizer and a crosslinking agent are added to the mixture, the mixture is poured onto a flat surface and crosslinked. The rare crosslinked film thus produced can be welded.

The film according to the invention can be widely used for packaging various chemicals and food in portions, where the packaging material decomposes in nature and does not pollute our environment.

Detailed description of the invention

The invention relates to a rare crosslinked polymer film consisting of polyvinyl alcohol, vegetable starch and water, as well as a plasticizer and a crosslinking agent.

The first component of the film according to the invention, apart from water, is therefore polyvinyl alcohol, which is obtained commercially. Commercial polyvinyl alcohol is never completely pure, since it is usually prepared from polyvinyl acetate by alkaline hydrolysis, which hydrolysis is not complete. According to the invention, polyvinyl alcohol with a degree of hydrolysis of, for example, 70-80% is preferably used. Polyvinyl alcohol can be characterized by the general formula (I),

CH ₂ --CH where n is the number of alcohol units in the polymer.

Another important raw material of the polymer film according to the invention is vegetable starch, which can be, for example - but not exclusively - wheat, corn, potato, rice, sago palm, etc. starch. Starches are plant-derived substances belonging to the polysaccharide family, and can be easily hydrolyzed into D-glucose. A colloidal solution is formed from starch in hot water, which solidifies as a gel when cooled. This starch is called starch.

Starch consists of two components, amylose and amylopectin. Amylose contains hundreds of glucose units linked by 1-4 α-glycosidic bonds. Due to the α-glycosidic bond, the molecules form a spiral-shaped helix. Formula (II) shows one turn of the helix.

O OH (Π)

The helix turns are held together by intramolecular hydrogen bonds.

-3A Another component of starch is amylopectin, which also consists of several hundred glucose units, but in these - unlike amylose - in addition to the 1-4 α-glycosidic bonds, 1-6 α-glycosidic bonds occur every 20-25 units. Because of this, amylopectin has a branched-loop structure, sometimes also with a helical structure.

According to the invention, wheat starch is preferably used, for example.

Any known polymer plasticizer can be used as a plasticizer for the polymer film according to the invention, such as glycerin, maltitol, sorbitol, xylitol, glycerol trioleate, glyceryl triacetate, polyethylene glycol, etc. Glycerin is preferably used according to the invention.

The rare cross-linked structure of the polymer of the invention is achieved by using a known cross-linking agent. Among the cross-linking agents, dialdehydes such as glutaraldehyde, succinaldehyde and the like are preferred.

In the polymer film according to the invention, the weight ratio of starch to polyvinyl alcohol is preferably between 1:5 and 5:1, more preferably between 1:1.5 and 1.5:1, the ratio of starch to glutaraldehyde is preferably between 1:1 and 100:1, more preferably between 10:1 and 20:1.

The invention also includes a process for producing the above-defined sparse crosslinked polymer film. The process is carried out by

- add the starch to cold water, then heat to boiling point while stirring continuously,

- mix the polyvinyl alcohol into cold water and heat it to boiling point while stirring constantly,

- the two mixtures are poured together and heated while stirring until a homogeneous mixture is obtained,

- let the mixture cool, then add the plasticizer,

- then we add the crosslinking agent,

- after mixing, the mixed polymer is placed under vacuum to remove any possible bubbles, the bubble-free mixture is poured onto a flat surface coated with Teflon and hot air is blown onto it until the remaining water is removed from the system,

- acid vapor is used to create the crosslink, the dried film is placed in a chamber filled with acid vapor. Under the influence of the acid, the crosslinking agent creates a rare crosslink.

According to the invention, it is preferable to add 5-25 parts by weight of starch to 100 parts by weight of water to prepare the starch solution. Preferably, for example, 6, 8, 10, 12, 14, 16, 18 or 20 parts by weight of starch is used for 100 parts by weight of water. To prepare the polyvinyl alcohol solution, 5-25 parts by weight of polyvinyl alcohol is used for 100 parts by weight of water, preferably for example, 6, 8, 10, 12, 14, 16, 18 or 20 parts by weight. For 100 parts by weight of the plasticizer, 0.5-12 parts by weight of the mixture of the two previous solutions is used. Preferably, for example, 0.6, 0.8, 1.0, 1.2, 1.5, 2 parts by weight of plasticizer is used.

For 100 parts by weight of the blended polymer prepared as above, 0.25 to 5 parts by weight of crosslinking agent is added. Preferably, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5 parts by weight of crosslinking agent are used.

The process can be represented by Scheme 1 below.

Hemiacetal

Acetal

Reaction scheme 1

-5In the first step, a hemiacetal is formed, which is converted to an acetal with the release of water by an additional -OH. This other -OH can be the OH group of the same PVA chain (as shown in the drawing), or of another chain, but this can also occur on the OH groups of the starch.

The other CHO group of the dialdehyde attaches to another PVA molecule in the same reaction, and the network is formed.

Acetal formation is reversible, so this network can be broken down relatively easily.

The finished film can be welded, thus allowing the dosing of a wide variety of substances, such as chemicals, nutrients, etc., in water-soluble packaging. Since the dissolution time of the film can be regulated according to the needs of the given application, the film according to the invention can be widely used.

The film according to the invention can be advantageously used, for example, for delivering water treatment chemicals into the water or in hobby fishing, where various plant seeds, corn, etc. can be added to the packaging material for the purpose of pre-feeding the fish.

The invention is illustrated by the following examples, but is not intended to be limited thereto.

Example 1

Add 10 g of household wheat starch (manufactured by: Klorid Chemical and Plastics Industry Co., Ltd.) to 100 g of water at 5 °C. The mixture is heated to 100 °C with slow stirring. At the same time, add 10 g of polyvinyl alcohol (manufactured by: Alcotex, 78% degree of hydrolysis) to 100 g of water at 5 °C. This mixture is also heated to 100 °C with slow stirring. The two solutions are poured together with continuous stirring and mixed until a homogeneous mixture is obtained. Add 1 g of glycerin to 100 g of the resulting solution, then add 0.5 g of glutaraldehyde in the form of a 25% aqueous solution to the resulting mixture.

The resulting polymer system is used to make the film on Teflon strips stretched on a glass plate. The samples are dried for 24 hours, and the dried film is placed in a chamber saturated with hydrochloric acid.

Glass transition temperature: Tg = 22.44 °C

Example 2

The procedure is as described in Example 1, except that 1.0 g of glutaraldehyde is added.

Example 3

The procedure is as described in Example 1, except that 1.5 g of glutaraldehyde is added.

Dissolution test

For the accelerated dissolution test, 10x10 mm samples are cut from the films prepared according to the above examples (5 pieces of each), these are weighed on an analytical balance, then placed in a 900 ml beaker, and 600 ml of distilled water is poured over them.

The dissolution test is performed with a Kika-werke Eurostar power control-visc type mixer. The speed of the mixing blade is 1000 rpm. The variation in the mass of the samples is due to the inaccuracy of the cutting.

The analysis of the samples according to Example 1 is shown in Table 1.

Table 1

1. sample according to example 1 2 3 4 5 Weight [g] 0.0338 0.0442 0.0363 0.0406 0.0383 T _water [°C] 19 18 19 19 17 ^dissolution time [hours/minutes] 16; 24 16; 50 16; 47 Γ 16; 40 16; 35

-6Dissolution time is approximately 16 hours 24 minutes to 16 hours 50 minutes.

The analysis of the samples according to Example 2 is shown in Table 2.

Table 2

2. sample according to example 1 2 3 4 5 Weight [g] 0.0446 0.0445 0.0443 0.0403 0.0442 Tvi _Z [°C] 15 16 15 14 15 ^dissolution time [orajpCFC] 24; 00 24; 20 24; 20 23; 40 25; 10

The dissolution time is approximately 24 hours to 25 hours 10 minutes.

The analysis of the sample according to Example 3 is shown in Table 3.

Table 3

3. sample according to example 1 2 3 4 5 Weight [g] 0.0459 0.0474 0.0369 0.0531 0.0475 Twater [°C] 17 18 17 19 17 ^dissolution time [θΓ3,ρ6Γθ] 30; 16 30; 30 29; 50 30; 40 30; 30

The dissolution time is approximately 29 hours 50 minutes to 30 hours 40 minutes.

We conducted comparative tests under identical conditions with the following:

Comparative sample 1: film made of pure polyvinyl alcohol (Alcotex PVA 78%). Thickness: 0.358 mm, weight: 0.04 g, water temperature 22 °C, dissolution time: t= 2 min 23 sec.

2nd comparison sample: foil available in a fishing shop (Type: Kamasaki PVA net, manufacturer: Advanced Carp. Equipment Ltd., Essex, UK) weight 0.04 grams, water temperature 22 °C), dissolution time, t = 58 sec.

The dissolution test clearly shows that the amount of crosslinker added to the polymer affects the dissolution time. A certain degree of inaccuracy in the time measurement (+/- 15 minutes) was accepted, as mixing was continued until the samples could no longer be seen with the naked eye.

The above data were measured in a sterile environment, where bacteria and microorganisms did not affect the dissolution of the polymer, and the dissolution was artificially accelerated by stirring.

We examined the dissolution of the film according to Example 1 in river mud water, in water infected with Coli bacteria and pectin-eating fungal spores. The test was carried out by placing a 10x10 mm piece of paper in a 20 ml Petri dish, then pouring 10 ml of concentrated infected water on it. After one day, the previously opaque film became transparent, lost its rigidity, and after 3 days, gelation was observed, the film was held with tweezers and it tore. After one or two weeks, the film was no longer visible to the naked eye.

The film produced according to Example 1, when placed in an aquarium, where a large number of microorganisms live, decomposes in approximately 48 hours.

We can therefore conclude that the film according to the invention degrades in natural waters within a controllable time.

Claims (8)

-7Patent claims 1. A thin crosslinked polymer film consisting of polyvinyl alcohol, vegetable starch and water, as well as a plasticizer and a crosslinking agent. 2. The film according to claim 1, which contains glycerin as a plasticizer. 3. The film according to claim 1 or 2, which comprises glutaraldehyde as crosslinking agent. 4. The film according to any one of claims 1-3, which comprises wheat starch as the starch. 5. The film according to any one of claims 1-4, wherein the weight ratio of starch to polyvinyl alcohol is preferably between 1:5 and 5:1, more preferably between 1:1.5 and 1.5 _:1 , and the ratio of starch to glutaraldehyde is preferably between 1:1 and 100:1, more preferably between 10:1 and 20:1. 6. A method for producing a film according to any one of claims 1-5, characterized in that the starch is added to cold water, and then heated to boiling point with continuous stirring, the polyvinyl alcohol is mixed into cold water, and then heated to boiling point with continuous stirring, - the two mixtures are poured together and heated while stirring until a homogeneous mixture is obtained, - let the mixture cool, then add the plasticizer, - then we add the crosslinking agent, - after mixing, the mixed polymer is placed under vacuum to remove any possible bubbles, - pour the bubble-removing mixture onto a flat Teflon-coated surface and blow warm air on it until the remaining water is removed from the system, - acid vapor is used to create the network, the dried film is placed in a chamber filled with acid vapor. 7. The method according to claim 6, characterized in that to prepare the starch solution, 5-25 parts by weight, preferably 5-12 parts by weight of starch are added to 100 parts by weight of water, to prepare the polyvinyl alcohol solution, 5-25 parts by weight, preferably 8-12 parts by weight of polyvinyl alcohol are added to 100 parts by weight of water, 0.5-12 parts by weight, preferably 0.8-1.2 parts by weight of plasticizer are added to 100 parts by weight of the mixture prepared from the two previous sides, and 0.25-/ parts by weight, preferably 0.3-2.5 parts by weight of crosslinking agent are added to 100 parts by weight of the mixed polymer prepared as above. 8. Use of a thin crosslinked polymer film according to any one of claims 1-5 or produced according to claim 6 or 7 for packaging chemicals, nutrients, such as water treatment chemicals or nutrients to be added to water in doses. ’ The use according to claim 8 for packaging the bait nutrient in portions for hobby fishing.