US1951940A - Process for making thin pressed fibrous articles - Google Patents

Description

March 20, 1934. G. J. MANSON 1,951,940

PROCESS FOR MAKING THIN PRESSED FIBROUS ARTICLES Original Filed Nov. 22, 1928 2 Sheets- Sheet 1 7 I I V 21 22 25 1L a 4 J1 TI.E.\

I I mm Bangui/mum March 20, 1934. a. J. MANSON 1,951,940

PROCESS FOR MAKING THIN PRESSED FIBROUS ARTICLES 7 Original Filed Nov. 22, 1928 2 Sheets-Sheet 2 Patented Mar. 20, 1934 PATENT OFFICE PROCESS FOR MAKING THIN PRESSED FIBROUS ARTICLES George James Manson, Hawkesbury, Ontario,

- Canada Application November 22, 1928, Serial No. 321,228 Renewed July 1'7, 1933 12 Claims.

This invention relates to improvements in the process for making thin pressd fibrous articles such as dishes, trays, food containers and the like, and the objects of the invention are to devise an improved process for making an article of this type having one or more smooth faces without discoloration or hydration of the fibrous stock.

A further object is to devise an improved process for making such an article without drainage markings on the surface thereof.

A further object is to devise an improved process for rendering such articles waterproof and grease-proof.

Pressed fibrous articles have been formed for some time of ,wood pulp principally by expelling the moisture from the pulp stock between suitable dies, the result being that an impression of the die surface usually having wire thereon, through which the moisture may escape, is left on the article.

Heat has in some instances been applied to facilitate the expulsion of moisture, but the heat has been applied under conditions, which cause the moisture to hydrate the surface fibres and discolour the article.

' The difficulty in avoiding hydration is greater when the article is thin, such as a dish or plate, as distinguished from a relatively thick sheet'of pulp stock.

I have discovered that a very much improved article may be produced, if before the final surface treatment by smooth dies, a large amount of the water content is removed, the final surface being finished by heat treatment with smooth dies.

The invention consists in the improved process as hereinafter more particularly described.

In the accompanying drawings is illustrated diagrammatically, a suitable apparatus for carrying out the improved process.

In the drawings:

Figure 1 shows a vertical section of a lower die used in the improved process.

Figure 2 is a similar section of the lower die showing a closure cap used therewith.

Figure Bis a vertical section of the lowe; die and an upper die cooperating therewith with a fibrous article in position between the dies.

Figure 4 is a vertical section showing a further step in the process in which the same lower die as shown in Figures 1, 2 and 3 cooperates with a heated upper die.

Figure 5 is a vertical section showing the final.

step in the process in which a heated lower die cooperates with an unheated upper die.

In the drawings like characters of reference indicate corresponding parts in the difierent figures.

The apparatus illustrated diagrammatically includes a lower die 10 which may be mounted in any suitable way for applying pressure thereto, such as the hydraulic ram 11.

This die 10 is provided with a forming surface 12- which is provided with drainage perforations 13 and below these perforations is a suction chamher 14 which has a suction pipe 15 communicating therewith.

Surrounding the lower die 10 and slidably mounted thereon is a cylindrical flange 16 which is normally urged upwardly in any suitable way, such as bysprings 17 so that in the position shown in Fig. 1 a reservoir 18 for the reception of liquid stock is provided above the lower die.

A closure cap 19 (see Fig. 2) is adapted to cooperate with the lower die 10 in one step of the process so as to close the reservoir 18 and a pressure pipe 20 extends through this cap and connects with a reservoir 18.

The usual wire mesh cloth 21 covers the forming face 12 of thelower die 10.

In the step in the process illustrated in Fig. 3 thelower die 10 cooperates with an upper die 22. In the step of the process illustrated in Fig. 4, the

, lower die 10 cooperates with an upper die 23 which upper die may be heated in any desired way and for purposes of illustration, in the form shown, the die 23 is provided with a heating chamber 24 to which maybe fed in any desired way a heating medium such as steam or oil.

'In the final step of the process illustrated in Fig. 5, the upper die 25 is unheated and a lower die 26 is heated in any desired way, such as explained in connection with the upper die 23 in Fig. 4, and in the form shown this die 26 is provided with a heating chamber 27.

A fibrous article such as a dish being formed within the apparatus is indicated by the numeral 28.

In making a thin pressed fibrous article in accordance with the improved process, the liquid stock which would contain about A to 2 fibre, is first fed into the reservoir 18 so as to cover the working face 12 of the lower die 10 as shown in Fig. 1 in which the level of the liquid stock is indicated by the broken line.

This liquid stock contains a suitable waterproofing substance which may be in the form of a wax emulsion containing about 2 to 4% of wax.

Any suitable grease-proofing substance is also incorporated to the liquid stock.

The lower die 10 is then moved into engagement with the closure cap 19 as illustrated in Fig. 2, and air pressure is led through the pipe 20, the pipe 15 being connected with the source of suction and in this step a large amount of the moisture is expelled so that the moisture content may be reduced to about 70%. Also in this step the article 28 is partially formed.

In the next step the lower die 10 carrying the article 28 is pressed against the upper die 22 (see Fig. 3) and the article is further formed and further moisture is expelled through the drainage perforations 13 in the lower die which moisture is exhausted through the suction pipe 15. At the completion of this step the article is relatively dry, about 45% of the moisture having been expelled.

At the end of the operation shown in Fig. 2, the article is about 20% to 25% pulp due to the air pressure on top. That is, the great bulk of the water has been expelled which makes the pressing operation in Fig. 3 much more simple. Instead of applying the cap 19 and air pressure I find that I may, in this stage, simply apply a strong suction to pipe 15 with atmospheric pressure on top.

In the next step the lower die 10 carrying the article 28 is pressed with substantial pressure against an upper die 23 (see Fig. 4) which die is heated to a relatively high temperature in any desired manner and this upper die 23 has a smooth heated face which produces, due to the heating and pressure, a smooth surface on the face of the article in contact with the upper die. In this step the steam or vapour generated is drawn ofi through the suction pipe 15.

At the completion of this step I have produced a thin pressed fibrous article which has one smooth face, which face is entirely free from drainage markings.

If it is desired that the article have both faces thereof smooth and free from drainage marks, it is subjected to a further step as illustrated in Fig. 5 in which the lower die 26, which has a smooth heated surface, is pressed against the article with substantial pressure so as to produce a smooth surface free from drainage markings on the face of the article in contact therewith so that at the completion of this final step shown in Fig. 5 I have produced a thin pressed fibrous article which has both faces thereof smooth and free from drainage markings.

In this last step since the faces of both the upper and lower dies 25 and 26 are smooth, it

would probably be necessary to provide some means for the escape of vapour and this could be done in any desired way, such for instance as imparting to the ram- 11 a vibratory motion so that the pressure between the dies would be intermittent and thus provide what is known as breathing of the die, so that this vapour might escape.

In my process a novel feature is that before the article is presented to a heated surface, a large amount of the water has been expelled therefrom by simple pressing operations with the article in the cold state and the article is not brought into contact with a heated surface until it is relatively dry. By thus having the article relatively dry before it is presented to a heated surface, the tendency to hydrate the fibres which results in discoloration of the article is entirely overcome, and it is found that the resulting article is not in any way discoloured.

Hitherto articles of this nature have been rendered waterproof and grease-proof by coating the article after it is completely formed with waterproofing and grease-proofing substances, but by my invention the waterproofing and greaseproofing substances are incorporated into the liquid stock before the article is formed, so that this waterproofing and grease-proofing is not in the nature of a coating but permeates the entire article.

If the article is pressed during drying so that the natural tendency of the fibres to swell while the moisture is leaving them is resisted, a more rigid article, having a harder and smoother surface isproduced. This applies to an ordinary unsized and non-waterproofed and non-greaseproofed article.

Now if the article has the waterproofing and grease-proofing materials incorporated with the liquid stock thereof and is dried as above, that is, if the article is pressed while it is hot, still moist and being dried, that is as the sizing materials (including both the waterproofing and grease-proofing materials) are being set, not only is the article given a harder and smoother surface as above but the sizing materials (including both the waterproofing and grease-proofing materials) are much more effective. The proposed treatment might be described as hot pressing the article while it is moist and the sizing materials (including both the Waterproofing and greaseproofing materials which have been incorporated in the liquid stock) are still unset. This is the treatment given the article in accordance with the improved process herein described and it has been found to produce exceptionally satisfactory results in the manufacture of thin wet-molded pressed fibrous articles such as dishes, trays, food containers.

I am aware that the. waterproofing and grease-proofing of paper has been hitherto carried out by incorporating the waterproofing and grease-proofing materials in the liquid stock, for instance as described in my previous U. S. Patent No. 1,762,931 granted June 10th, 1930, application for which was filed on March 14th, 1927, but suchprevious process relates to the manufacture of paper as made in the ordinary paper making machines and does not relate to the manufacture of what may be termed a wet-molded" article as in the present case and the functioning of the process and the results produced are very radically different. In this previous process there is no suggestion of hot pressing while the paper is moist and the size unset.

From the foregoing it will be apparent that I have devised an improved process for making 1 thin pressed fibrous articles whereby the objects of my invention have been attained.

It is to be understood that the drawings are purely diagrammatic and that I do not wish to confine my invention to the particular form of apparatus shown.

Various modifications may be made in my invention without departing from the spirit thereof or the scope of the claims and therefore the exact forms of apparatus shown and described 1 are'to be taken as illustrative only and not in a a limiting sense, and I desire that only such limitations be placed thereon as shall be imposed by the prior art or are specifically set forth in the claims.

What I claim as my invention is:

1. The method of forming a pressed fibrous article which comprises first expelling a large amount ofwater therefrom while cold by simple pressure and the passage of I air transversely through the article and subsequently subjecting the article to a further drying action by heat and under mechanical pressure while simultaneously subjecting the article to suction.

2. The method of forming a pressed fibrous article which comprises first expelling at least 45% of the water therefrom while cold by simple pressure and the passage of air transversely through the article and subsequently subjecting the article to a further drying action by heat and under mechanical pressure while simultaneously subjecting the article to suction.

3. The method of forming a thin pressed fibrous article which comprises first expelling a large amount .of water therefrom while cold by pressing and subsequently subjecting the article to a further drying action by heat and under mechanical pressure while simultaneously subjecting the article to suction.

4. The method of making a waterproof fibrous article from liquid stock which comprises incorporating a water-proofing substance in the liquid stock, then initially forming the article by pressure and expelling a large amount of water theretherefrom while cold, and then hot pressing the article while it is still moist and the waterproofing material is still unset.

5. The method of making a waterproof fibrous article from liquid stock which consists in adding- Wax in the form of an emulsion to the liquid stock, then initially forming the article by pressure an expelling a large amount of water therefrom while cold, and then hot pressing the formed article while it is still moist and the wax unset.

6. The method of making a waterproof fibrous article from liquid stock which consists in adding an emulsion containing 2% to 4% wax to the liquid stock, then initially forming the article by pressure and expelling a large amount of moisture therefrom while cold, and then hot pressing the formed article while it is still moist and the wax unset.

7. The method of making a grease proof fibrous article from liquid stock which consists in adding a grease-proofing substance to the liquid stock, then initially forming the article and the passage of air transversely through the article, and subsequently subjecting the article to further drying action by heat and under mechanical pressure while simultaneously subjecting the article to suction.

' 9. The method of making a grease-proofing fibrous article from liquid stock, which comprises incorporating a grease-proofing substance in the liquid stock, then expelling a large amount of water therefrom while cold by simple pressure and the passage of air transversely through the article, and subsequently subjecting the article to further drying action by heat and under mechanical pressure while simultaneously subjecting the article to suction.

10. The method of forming a fibrous article which comprises initially forming the article in aperforated forming die, subjecting the article to mechanical pressure between unheated perforated forming dies and simultaneously therewith causing a flow of air transversely through the dies and article under pressure therebetween, and then subjecting the article to a further drying operation by mechanical pressure in a heated die while exhausting by suction the vapor generated.

11. The herein described method of forming a pressed fibrous article which comprises initially forming the article from liquid stock by pressure in a forming die, then expelling a large amount of moisture from the initially formed wet and unheated article by mechanical pressure thereof between unheated perforated dies and by simultaneously with said mechanical pressure exerting air pressure on one side of the die and suction on the other side thereof whereby air under normal temperature conditions and in the absence of any heating action on the article is forced transversely through the dies and article under pressure therebetween and prior to any heating of the article, and finally subjecting the article to a further drying operation with heat and pressure in a smooth die. 1

12. The herein described method of forming a pressed fibrous article which comprisesinitially forming the article from liquid stock by pressure in a forming die, then expelling a large amount of moisture from the initially formed wet and unheated article by mechanical pressure thereof between unheated perforated dies and by simultaneously with said mechanical pressure exerting air pressure on one side of the die and suction on the other side thereof whereby air under normal temperature conditions and in the absence of any heating actionon the article is forced transversely through the dies and article under pressure therebetween and prior to any heating of the article, then subjecting the article to a further drying operation with heat and pressure in a smooth die, and exhausting by suction the vapor generated.

GEORGE JAMES MANSON.

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