US2142718A - Manufacture of artificial materials - Google Patents

Description

Jan. 3, 1939. H DFQEYFUS 2,142,718

MANUFACTURE OF ARTIVFICRIAL MATERIALS Filed Feb. 4, 1.936

Y HG2 A3/ 7 5222 U A 36 i 32 6\2I0 2|/ m `/23934 Patented Jan. 3, 1939 MANUFACTURE OF ARTIFICIAL MATERIALS Henry Dreyfus, London, England Application February 4, 1936, Serial No. 62,331 In Great Britain March 2, 1935 4 Claims.

This invention relates to improvements in the treatment of artificial materials, and particularly to improved methods and apparatus for the stretching of artificial foils, films and similar materials.

U. S. applications S. Nos. 4,510 and 4,511, both filed on February l, 1935, describe inter alia processes for the treatment of artificial foils, films and similar materials, hereinafter referred to generically as films, wherein they are stretched in the presence of steam or hot water during their travel from one point to another in order to improve their tensile strength. The present invention relates to improvements in such processes and to novel apparatus for the carrying out of such improved processes.

According to the present invention the stretching of artificial films in the presence of steam or hot water is effected in a plurality of stages during their travel from one point to another. InY this manner products having improved mechanical properties may be obtained, particularly when a considerable degree of stretch is to be produced. Moreover by the process and apparatus of the present invention the stretching of films to a considerable extent may be facilitated and the tendency to lateral deformation may be reduced. The films may be subjected to a stretching tension during the whole of the stretching operation, or such tension may be removed during a part or parts of the operation, so that between stages at which stretch is applied are stages during which the lm is not stretched, but travels forward without its length being increased. Such stages will hereinafter be referred to as rest stages.

While the invention includes the stretching of artificial films, sheets and all similar materials, it is particularly concerned with the stretching of foils such as are employed for packaging purposes, since it is of particular importance that such materials should be thin and yet should possess a high tensile strength.

The present invention is particularly concerned with stretching films in the presence of wet or saturated steam or hot water at a temperature above 100 C., and especially above 120 C. since, in general, it is found that the most satisfactory results are obtained under such conditions. Steam or hot water at lower temperatures, e. g. 95 C., may however be employed. For details regarding the temperature, pressure and other conditions under which the steam or hot water may be employed reference is made to U. S. ap-

plications S. Nos. 4,510 and 4,511, referred to above.

In carrying out the process according to the present inventionthe films may travel from a roll or other source of supply to a feed :device ,5, and thence to suitable stretching devices, positioned in a vessel containing steam or hot Water, which effect stretching in a yplurality of stages with or without intermediate rest stages. The feed device may be contained in the stretch- I0 ing vessel, but is preferably outside it. After issuing from the stretching vessel lthe film may pass in contact with a positively driven forwarding device and thence to a roll or other take-up device. When stretching is carried out in the 15 presence of hot water, the lms are preferably immersed in the Water during the Whole of their travel through the stretching vessel.

When steam is employed, it may be introduced by means of one or more orifices positioned in 20 the vessel. Preferably, it is projected directly on to the films across their whole width and on both sides from orices close to the films. It is also desirable that such direct application should be eifected during each stage of stretching. ,f

The rst roller or other device of the stretching mechanism may forward the film at the same speed as that at which it enters the stretching vessel so that no stretch is effected until the film has passed this roller or other device, or the roller or other device may forward the film at a greater speed so that stretching is effected before the film reaches the rst roller or other device. Stretching may be longitudinal only, i. e. in the direction of travel of the lm, or a lateral tension may also be applied, such tension being suiiicient to stretch the film laterally also or sufcient only to prevent or control lateral shrinkage under the action of the longitudinal stretching tension.

The lm may pass directly from the external atmosphere into the stretching vessel, or it may pass into the stretching vessel from a chamber containing air or other suitable inert fluid maintained at any required pressure or temperature. Alternatively, or in addition, it may pass into a similar chamber on issuing from the stretching vessel. By this means any tension 0n the film due to escape of steam or hot water through the inlet or outlet orices for the film may be reduced or substantially completely eliminated and the characteristics of the product obtained may be controlled. Processes wherein such end chambers are employed and apparatus for carrying out such processes are described in U. S. application S. No. 17,242, filed April 19, 1935, to which reference is made for details with regard to the construction and use of the end chambers.

An apparatus according to the invention for stretching artificial lms in the presence of steam comprises a rectangular vessel having a width slightly greater than the width of the film which it is proposed to treat, and a suitable length, for example 6 to 10 feet. The vessel consists of two portions, a detachable, flanged, box-like lid and a box-like bottom portion having corresponding flanges to which the lid is xed, so that a substantially steam-tight joint is obtained. In the ends of the two portions rollers are rotatably mounted, the method of their mounting or the material of which they are made being such that it is just possible for the lm to pass easily bpetween them while leakage of steam around the film is substantially avoided. For example, rubber rollers may be employed, or alternatively incompressible rollers carried in bearings sliding in vertical guides and forced together by springs inserted behind the bearings may be used. Inside the bottom portion of the vessel are mounted driven rollers extending across the Width of the vessel and preferably close together, for example having their adjacent surfaces only about 1A; or 1/2 an inch apart. The rollers are arranged in two sets, those of one set being above those of the other, so that the film passes under the lower rollers and over the upper ones. With this arrangement the film may lap round a considerable portion of the surface of each roller and slip may be avoided. Each roller is positively driven so that the rates of rotation of the different rollers may be varied as desired. Thus, on starting up, the rollers may be all rotated at the same peripheral speed until the lm has reached a satisfactory condition for stretching, when the rollers may be rotated at successively increasing speeds until the desired degree of stretching is obtained. Each roller may be rotated at a peripheral speed greater than that of the roller preceding it, so that a stretch is applied to the film which extends along the whole length of its travel between the first and last stretching rollers, or, if desired, as described above, rest stages may be inserted by rotating one or more pairs of adjacent rollers at the same peripheral speed. Steam is introduced into the vessel by means of steam pipes extending across its width and arranged close to the lm so that steam is projected directly on to each side of the film before the initial stretching roller and between each of the subsequent rollers. The apparatus may also comprise a pressure gauge, a pressure release valve, a steam trap and a temperature indicator.

The apparatus may also comprise means for stretching the lm laterally or preventing it from shrinking under the longitudinal tension. Such means may consist of a series of pairs of rollers, having their axes normal to the length of the lm or suitably inclined thereto, between wln'ch the film is gripped, or a pair of endless bands on each side of the film which gripthe edges. Suitable apparatus for applying a lateral tension is described in U. S. application S. No. 666,656 filed April 18, 1933.

A similar form of apparatus with suitable modiflcations may be employed for stretching in the presence of hot water.

The invention also includes processes and apparatus for stretching artificial films wherein perforated drums are employed into which steam, hot water or other stretch-assisting agent is introduced internally, so that the stretch-assisting agent reaches that surface of the film which is actually in contact with the drums and also issues into the vessel through the holes which are not covered by the film. Such drums may be employed in any stretching operation, whether it is carried out in a plurality of stages, as described in the present specication, or in a single stage. Moreover, besides being introduced into the interior of the perforated drums, the stretchassist ing agent may also, if desired, be introduced at other points in the vessel, for example by means of perforated pipes extending across the vessel. Alternatively such pipes or the like may be the sole means of introducing the stretch-assisting.

agent into the vessel, since the perforations in the drums render it possible for the agent to reach that surface of the film in contact with the drums, whether or not the stretch-assisting agent is introduced directly into the interior of the drums.

Examples of apparatus according to the present invention are illustrated in the accompanying drawing wherein Fig. 1 is a cross-sectional elevation of an apparatus containing a plurality of stretching rollers for stretching in the presence of steam;

Fig. 2 is .a similar view of an apparatus for Y stretching in the presence of hot water; and

Fig. 3 is a side elevation of a stretching roller having means for the introduction of steam internally.

In Fig. 1 the stretching vessel 4 consists of a box-like bottom portion 5 and a lid portion 6. In the ends of the lid and box are rollers 1, 9 and 8, I0 respectively, which are rotatably carried in bearings slidable vertically in guides formed in the end wall of the box and lid and which are forced together when the box and lid are in position by means of springs carried in the guides above the bearings in the lid and below those in the box. The edges of the sides and ends of the box and lid are anged except in the portions where the rollers are mounted so that the box and lid can be held together by means of bolts and wing nuts or other suitable fixing devices. f

Inside the box portion of the. vessel are an upper series of rollers 20, 2|, 22 and 23 and a lower series 24, 25 and 26 which are rotatably mounted andv which are positively driven by infinitely variable gearing tted to the outside of the vessel. Steam is introduced into the vessel through steam pipes II, I2, I3 and I4 which extend across the whole width of the vessel. Steam is supplied to these pipes through headers I5 and I6 which are connected to the steam main (not shown). The steam pipes II and I2 are perforated or slotted so that the steam emerging from them is directed vertically downwards' and upwards respectively directly on` to the lm, while pipes I3 and I2 are perforated or slotted so that steam is projected from both sides of them on to the adjacent film. A pressure gauge I'I, a steam trap I8 and a safety valve I9 are also provided.

Fig. 2 illustrates a similar apparatus adapted forY use with hot water under pressure. As in the case of the apparatus illustrated in Fig. 1 it comprises a vessel 4 having flanged box and lid portions 5 and 6, tted at the ends with rollers 1, 8, 9, I0. Two series of stretching rollers 2U, 2I, 22, 23, 24, 25 and 26 are mounted inside the box portion. Instead of the steam pipes illustrated' in Fig. 1 the apparatus comprises a water inlet 5l, a water outlet 52 and a steam heating coil 53 for maintaining the require-d temperature. The apparatus also comprises a pressure gauge il, a drain pipe and valve 5A and catch trays 55 to catch any water. escaping through the rollers 7, 8, 9 and l0.

Fig. 3 is a side elevation of a cylindrical drum 49, the sides of which are perforated with a large number of small holes M. One axis 42 of the drum is formed from a hollow tube 43 which extends into the interior of they drum, and which is perforated or slotted so that steam can be blown through it into the interior of the drum.

In carrying out the process of the invention with the apparatus illustrated in Fig. 1 a lm 3@ proceeding from a suitable supply 3l passes rst round a feed device consisting of two positively driven rollers 32, 33, which control its rate of travel, then between the rollers 'l and 8 into the stretching vessel where it passes round the two series of stretching rollers 2li-23 and 2li- 26 to the other end of the vessel. Here it emerges through the. rollers 9 and lil, passes round a forwarding device consisting of two .positively driven rollers 34, 35, and thence to a take-up device 36. The stretching rollers in the stretching vessel may be either driven at continuously increasing peripheral speeds so that stretching' is effected between each pair of rollers, or one. or more pairs of adjacent rollers may be driven at the same peripheral speed so that no stretch is effected between the pair or pairs. The first roller 2li may either be driven at the. same speed as the roller 33 so that no stretching is effected until after the iilm has passed roller or it may be driven at a. higher speed than the roller 33 so that stretching is effected between these two rollers. Similarly stretching may or may not be effected between the roller 23 and the roller 34.

Any tendency for condensed steam to collect in the angles made by the iilm with the bottom rollers 24, 25 and 26 may be reduced by tilting the vessel so that the axes of these rollers are inclined to the horizontal. n

The present invention is of particular importance in the stretching of artificial lms containing cellulose acetate, but vit may also be employed in the stretching of such materials containing other derivatives of cellulose, for example cellulose formate, cellulose propionate, cellulose butyrate, cellulose nitro-acetate, cellulose nitrate and other esters or mixed esters of cellulose, cellulose ethers or mixed ethers, for example methyl, ethyl and benzyl cellulose, and cellulose ether-esters, for example ethyl cellulose acetate and Oxy-ethyl cellulose acetate. Other articial lms may also be stretched according to the present invention, for example, lms having a basis of regenerated cellulose obtained by the viscose process, or of polymerized vinyl compounds or other film-forming bases.

Having described my invention what I desire to secure by Letters Patent isz- 1. Process for improving the properties of articial films having a basis of an organic derivative of cellulose, which comprises stretching them in a plurality of stages in the presence of a hot aqueous luid at a temperature above 100 C. during their travel from one point to another and directing hot aqueous iiuid at a temperature above 100 C. on to the iilms during each stage of stretching.

2. Process for improving the properties of articial lms having a basis of an organic derivative of cellulose, which comprises stretching them in a plurality of stages in the presence of wet steam at a temperature above 100 C. during their travel from one point to another, and directing wet steam at a temperature above 100 C. on to the lms during each stage of stretching.

3. Process for improving the properties of artificial films having a basis of cellulose acetate, which comprises stretching them in a plurality of stages in the presence of wet steam at a temperature above 120 C. during their travel from one point to another, and directing wet steam at a temperature above 120 C. on to the films during each stage of stretching.

4. Process for improving the properties of artilicial films having a basis of an organic derivative of cellulose, which comprises str-etching them in a plurality of stages in the presence of wet steam at a temperature above 100 C. during their travel from one point to another, and directing wet steam at a temperature above 100 C; on to each side of the films during each stage of stretching.

HENRY DREYFUS.

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