US2784116A

US2784116A - Coating process for regenerated cellulose foils

Info

Publication number: US2784116A
Application number: US498108A
Authority: US
Inventors: Lakatos Eduard; Schneglberger Kurt; Greune Heinrich; Heyna Johannes
Original assignee: Kalle GmbH and Co KG
Current assignee: Kalle GmbH and Co KG
Priority date: 1954-03-31
Filing date: 1955-03-30
Publication date: 1957-03-05
Anticipated expiration: 1974-03-05
Also published as: GB782455A; FR1121423A; DE1045866B

Description

COATHN'G PROCESS FDR REGENERATED CELLULOSE FOILS No Drawing. Application March 30, 1955, Serial No. 498,108

Claims priority, application Germany March 31, 1954 12 Claims. (Cl. 117-144) The present if'ivention relates to foils of regenerated cellulose provided with a coating for the purpose of improving the foils fastness to moisture as well as its tightness to gases. More particularly the invention relates to a process of enhancing the adhesion of the coating to the surface of the foil of regenerated cellulose by a chemical treatment of the foil before coating it.

In order to produce so-called moisture-proof foils of regenerated cellulose, also called moisture-proof cellulose hydrate foils, the regenerated cellulose foils are coated with a moisture-proofing water-repellent film. Preferably such coatings are used that have hot-sealing properties. Usually the foil is impregnated with a socalled anchoring agent before being coated for the purpose of increasing the adhesion of the coating to the foil. As a further advantage of using said anchoring agent the coating does not peel ofi. from the base foil even when the moisture-proofed foil is exposed for a longer period of time to the influence of water or wet substances.

Principally, there are two possibilities of impregnating the foil with the anchoring agent:

(a) In connection with the production proceedings and before it enters the drying chamber, the foil is passed through a bath in which the anchoring agent is dissolved.

ttes Patent Usually, the anchoring agent is added to the bath containing the softening agent, e. g. glycerol.

(b) Or the finished foil, i. e. the dried and rolled up foil, is impregnated by a separate dipping or spraying operation with the solution of the anchoring agent, and subsequently dried.

By coating foils thus provided with an anchoring agent moisture-proof cellulose hydrate foils are obtained which are especially suited for packaging either wet goods, such as jam, meat etc; which must be prevented as far as possible from losing moisture, or substances detrimentally affected by moisture which must be protected against the influence of atmospheric dampness or condensed humidity.

Almost all of the anchoring agents hitherto known are suited only for the second method sub (b), in which the treatment of t foil with the anchoring agent is a separate process step and which is therefore more ex pensive and more troublesome than the other method, for which suitable anchoring agents have been lacking so far.

The present invention is concerned with a process for producing coated regenerated cellulose foils according to which process the foils can be impregnated with the anchoring agent in a satisfactory degree also during their production, before drying. The process is characterized in that the cellulose hydrate foils are impregnated with anchoring agents which are water-soluble reaction products selected from the group consisting of reaction products of phosphorous oxychloride (POCls) and alkylene imines and reaction products of phosphorous thiochloride (PSCls) and alkylene imines. For the produc- 2,784,116 Patented Mar. 5, 1957- tion of the reaction products to be used according to the present invention as anchoring agents there may be also used mixtures of alkylene imines with secondary aliphatic amines,'such as dimethyl amine and diethyl amine, with the alkylene imine component predominating in said mixture; advantageously the quantity of alkylene imine should be twice or more that of secondary amine.

The anchoring agents to be used according to the present invention may be monomeric reaction products of the components in question, or they may be low degree polymerisation products that are still water-soluble. The monomeric reaction products may be prepared for instance by reacting phosphorous oxychloride or phosphorous thiochloride with alkylene imines, such as ethylene imine, in the presence of acid-binding agents. In this reaction, instead of using pure alkylene imine, part of said alkylene imine may be substituted by secondary aliphatic amines, such as dimethyl amine or diethyl amine, thus producingcompounds which may contain, for instance, 1 mol secondary aliphatic amine and 2 moles alkylene imine for each phosphorus atom present. The reaction is suitably performed while using solvents as reaction medium. Suitable solvents are aliphatic or aromatic hydrocarbons, or chlorinated hydrocarbons, such as for instance chloroform, benzene,-toluene, chlorobenzene and similar solvents. Tertiary amines, such as trimethyl amine or triethyl amine, and especially anhydrous ammonia, may be used as acid-binding agents. By the application of mild polymerisation conditions, the monomeric reaction products thus obtained can be polymerised to such a degree as to be still water-soluble.v

Such polymerisation may be brought about, for instance, by heating to a higher temperature, up to C. The length of the heating period depends upon the desired degree of polymerisation. When lower temperatures are applied, the reaction will take a longer time. Or polymerisation may be brought about by means of catalysts. Suitable catalysts may be, for instance: (a) acid catalysts, such as sulfuric acids, sulfurous acid, or carbonic acid;

(b) dialkyl sulfates, such as dimethyl sulfate, diethyl sulfate, dipropyl sulfate or dibutyl sulfate; (0) p-toluenesulfonic acid alkyl esters, such as the methyl and the ethyl ester, and similar compounds; (d) water and other 7 catalysts. Solvents may or may not be used in the poly v merisation process.

benzene, toluene or xylene are suitably used as solvents.

Aromatic hydrocarbons, such as The polymerisation process can be easily watchedby taking samples of the reaction mixture or by making water-solubility or viscosity tests. If necessary, the polymeric compounds may be separated fromthe monomeric compounds still present by adding suitable diluents. Such diluents may be, for instance, aromatic hydrocarbons, such as benzene or toluene, or ketones, such as acetone etc. Upon adding the diluent to the reaction mixture, the polymerisation product precipitates in the form of a solid, white substance. Various methods for preparing such compounds are specifically described on pages 210-232 in Liebigs Annalen der Chemie, vol. 566 (1950), by Herbert Bestian.

discussed on page 215. Such methods are also disclosed in German Patents No. 863,055, dated January 15, 1953,

and No. 888,853, dated September 7, 1953.

In order to obtain the desired degree of impregnation" of the regenerated cellulose foil the reaction products according to the present invention can be used individually or said reaction products can be applied in mixture with each other.

The impregnation of the cellulose hydrate foils is ad- The particularly relevant" disclosures are to be found onpages 231 and 232, which describe the preparation of compounds XIII and XIV ta thiochloride and alkylene imines to one of the usual aqueous baths through which the foil band passes in p the course of its production, for instance to the bath containing the softening agent, Equallygood results are obtained when the foil, after. it is dried, is impregnated with the anchoring agent by passing the dry foil through a solution of the reaction product in organic solvents. Ethyl alcohol and methyl alcohol are very well suited as solvents for the anchoring agent. I

Frequently, the impregnating effect of the anchoring agent may be increased by adding to the impregnating bath acids acting as catalysts. Such acids may be, for instance, boric acid, lactic acid, glycolic acid, citric acid, gallic acid, succinic acid or maleic acid, or a salt showing acid reaction in aqueous solution may be used, such as monosodium phosphate or monokaliurn phthalate. Or the foil may be submitted to a treatment with an acid or an acid reacting salt after it has been coated with the reaction products of phosphorous oxychloride or phosphorous thiochloride respectively, and alkylene imines. Care must be taken that the solution containing the acid catalyst is not removed by the impregnating solution if the catalyst is applied before impregnating the foil, or, vice verse, that it does not decrease the already established impregnation effect, in case that the acid catalyst is applied after impregnating the foil. In the first case, it is advisable to spray the impregnating: solution of the anchoring agent upon the foil after it has been treated with the acid catalyst in a dipping bath; in the latter case, it is advantageous to spray a solution of the catalyst on the foil after it has been steeped in the impregnating bath.

Another method of anchoring the coating to the base foil is by adding the anchoring agent of the present invention to the coating composition. effect thus obtained may be further increased by treating the foil with a solution of an acid catalyst before it is coated. For this purpose, the acid catalyst is suitably added to the softening bath.

The following examples are inserted in order to illustrate the present invention without an intention of limiting the invention to what is stated in the examples.

Examples (1) After the usual treatment in the wet section of a spinning or casting machine, a cellulose foil produced by regeneration from viscose or a cuprammonium solution is passed through a softening bath consisting of an aqueous solution containing 6% glycerol and 0.2% of a reaction product of phosphorous oxychloride and ethylene imine, said reaction product having undergone some polymerisation. The impregnated foil is dried and rolled up. It is then coated with a known coating composition which may, for instance, contain:

dissolved in a 1:1 mixture of acetic ester and benzene.

After drying the coated foil is moisture-proof andthe' coating does not peel off from the foil even after several months storage under water.

The anchoring (2) The procedure described in Example 1' is followed.

The softening bath consists of water in which are dissolved 8% of ethylene glycol and 0.2% of a reaction product of phosphorous thiochloride and ethylene imine'.

The foil is coated according to the method described in Example 1. The moisture-proofed foil is resistant to water for several months and may even be heated to boiling-without the coating peeling oif.

1(3) The method described in Example 1 is followed.

i The softening bath consists of water containing 8% i ethylene glycol and 0.2% of the reaction mixture of 1 mol phosphorous oxychloride, 1 mol diethyl amine, and 2 moles of ethylene imine. The moisture-proofed foil is also excellently water-resistant and boil-fast.

(4) A dried regenerated cellulose foil made according to the viscose process or the cupramrnonium process is passed through an ethyl alcohol (96%) bath containing 0.5% of a mixture consisting of equal parts of a re action product of phosphorous oxychloride and ethylene imine, said reaction product having undergone some polymerisation, and a monomeric reaction product of phosphorous thiochloride and ethylene imine. After drying the impregnated foil is coated with a coating composition corresponding to the one described in Example 1. The moisture-proof regenerated cellulose foil thus produced is water-resistant and boil-fast.

(5) Using a softening bath which contains 6% of ethylene glycol, 0.2% of a reaction product of phosphorous oxychloride and ethylene imine, the reaction product having suffered some polymerisation, and 0.05% of gallic acid dissolved in water, a cellulose hydrate foil is impregnated and coatedas described in Example 1. The moisture-proof cellulose hydrate foil thus obtained is excellently resistant to cold and boiling water.

(6) A regenerated cellulose foil is passed through a softening bath containing 6% of glycerol and 0.1% of glycolic acid dissolved in water. After drying, the foil is coated with a coating composition comprising in addition to the components stated in Example 1 0.5 part by weight of a reaction product of phosphorous oxychloride and ethylene imine. The foil thus coated is water-resistant and boil-fast.

What We claim is:

l. The process of coating a foil of regenerated cellulose comprising the impregnation of the foil with a watersoluble reaction product selected from the group consisting of reaction products of phosphorousoxychloride and alkylene imines and reaction products of phosphorous thiochloride and alkylene imines before the foil is coated.

2. The process described in claim 1 wherein the impregnation of the foil with said water-soluble reaction product is obtained by adding said reaction product to an aqueous treating bath.

3. The process described in claim 2 wherein said water-soluble reaction product for the impregnation of the foil is added to the bath containing the softening agent.

4. The process described in claim 1 wherein the impregnation of the foil with said water-soluble reaction product is practiced after the regenerated foil is dried and before it is coated.

5. The process described in claim 1 wherein said water-soluble reaction product contains as an admixture a water-soluble reaction product selected from the group consisting of reaction products of phosphorous oxychloride and secondary aliphatic amines and reaction products of phosphorous thiochloride and secondary aliphatic amines.

6. The process of coating a foil of regenerated cellulose comprising the impregnation of the foil with a watersoluble reaction product selected from the group consisting of reaction products of phosphorous oxychloride and alkylene imines and reaction products of phosphorous thiochloride and alkylene imines in the presence of'an acid substance selected from the group consisting of acids and salts showing an acid reaction in aqueous solution, said impregnation being effected before the foil is coated.

7. The process described in claim 6 wherein said acid substance is a water-soluble organic acid.

8. The process described in claim 6 wherein the foil is treated with said acid substance before said impregnation with said water-soluble reaction product takes place.

9. The process described in claim 6 wherein the foil is treated with said acid substance after said impregnation with said water soluble reaction product has taken tri-place and before the foilis coated.

h la.)

10. The process of coating a foil of regenerated cellulose wherein a coating preparation is used containing as a component of the mixture a water-soluble reaction product selected from the group consisting of reaction products of phosporous oxychloride and alkylene imines and reaction products of phosphorous thiochloride and alkylene imines.

11. The process described in claim 10 wherein said water-soluble reaction product contains :as an admixture a water-soluble reaction product selected from the group consisting of reaction products of phosphorous oxychloride and secondary aliphatic amines and reaction products of phosphorous thiochloride and secondary aliphatic amines.

12. The process described in claim 10 wherein a foil of regenerated cellulose is coated which has been treated before the coating operation with an acid substance selected from the group consisting of acids and salts showing an acid reaction in aqueous solution.

References Cited in the file of this patent UNITED STATES PATENTS 1,857,163 Platt May 10, 1932 2,606,900 Parker Aug. 12, 1952 2,654,738 Lecher Oct. 8, 1953 2,698,793 IJandes Ian. 4, 1955

Claims

6. THE PROCESS OF COATING A FOIL OF REGENERATED CELLULOSE COMPRISING THE IMPREGNATION OF THE FOIL WITH A WATERSOLUBLE REACTION PRODUCT SELECTED FROM THE GROUP CONSISTING OF REACTION PRODUCTS OF PHOSPHOROUS OXYCHLORIDE AND ALKYLENE IMINES AND REACTION PRODUCTS OF PHOSPHOROUS THIOCHLORIDE AND ALKYLENE IMINES IN THE PRESENCE OF AN ACID SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF ACIDS AND SALTS SHOWING AN ACID REACTION IN AQUEOUS SOLUTION, SAID IMPREGNATION BEING EFFECTED BEFORE THE FOIL IS COATED.