WO2018138731A1

WO2018138731A1 - System for manufacture of adhesive tapes

Info

Publication number: WO2018138731A1
Application number: PCT/IN2017/050094
Authority: WO
Inventors: Shrikant Prabhakar ATHAVALE
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-01-24
Filing date: 2017-03-16
Publication date: 2018-08-02
Anticipated expiration: 2019-07-24

Abstract

Described is an integrated system and a process for manufacture of paper-based adhesive tapes which results in cost savings and increases the efficiency of the manufacturing process.

Description

SY ST E M FOR MANU FACT UR E OF ADH E SIV E TAPE S

FIE L D OF INV E NTION

This disclosure is related to methods and systems for manufacture of paper based adhesive tapes.

BAC K G ROUND OF T H E INV E NTION

Paper based adhesive tapes have wide applications including and not limited to their use as masking tapes, electrical insulation grade paper tapes, cast graphics filmsAapes with self adhesives, as fabrics, foil, or silicone coated paper liners and the like. Generally, the production of such tapes is conducted across multiple facilities. For example, the creped paper is generated at one site, the paper is then printed at a different site, the printed paper is then coated with release films at a third site, the adhesive coating is typically placed on the tape at a fourth site.

There is a need in the field for efficient and cost effective methods for manufacture of paper based adhesive tapes.

SUM MARY OF T H E INV E NTION

Provi ded herei n are systems and processes for manufacture of paper-based adhesive tapes.

In particular, the systems and processes described herein allow for one-pass production of paper- based adhesive tapes, thereby avoiding the need for using multiple sites for various steps of the manufacturing process.

In a first aspect, provided herein is an integrated system for manufacture of paper- based adhesive tapes comprisi ng

(i) a first module for saturation coating and creping paper; ( i i ) a second modul e for pri nti ng a mark on a f i rst si de of the paper obtai ned from the first module;

( i i i ) a thi rd modul e for coati ng sai d pri nted f i rst si de of sai d paper obtai ned from the second module with a release coating;

( i v) a fourth modul e for coati ng the second si de of the paper obtai ned from the thi rd module with a pressure sensitive adhesive; and

(v) optionally, cutting the paper into desired widths.

In one embodiment, the integrated system described above is a one pass system which reduces overall waste by up to 10% based on starting material when compared to manufacturing wherein each module described above is operated separately. In one embodiment, the manufacturing of paper-based adhesive tapes is substantially water based. In some embodiments, the saturation coating is conducted with an aqueous mixture of latex. In some embodiments, the latex is naturally occurring latex or synthetic latex. In some embodiments, the first module further comprises rollers for squeezing the saturation coated paper In some embodi ments, the f i rst modul e further compri ses heated di rect contact drum dryers for dry i ng the squeezed saturation coated paper. In some embodiments, the heated direct contact drum dryers are heated by circulation of hot water. In some embodiments, the fourth module comprises a G ravure rol I coati ng system and a Myer bar meteri ng system

In a group of embodiments, the system further comprises a drying tunnel and a rewind station. In some embodiments, the system is operated using solar energy. In some embodiments, the system is operated using electricity from a power grid.

In a group of embodiments, a single pass in the system provides the latex coating and creping, the printing of a mark, the coating of a release coat, and the adhesive coating to provide a paper-based adhesive tape product

In another aspect, provided herein is an integrated process for manufacture of paper based adhesive tapes comprising:

(i) initiating the unwinding of a roll of paper which is placed on a drum;

(ii) dipping the paper, as it is unwound, into an aqueous solution of latex to obtain a latex saturated paper;

(iii) squeezing out the excess latex from the latex-saturated paper of step (ii) by running the paper between rollers;

(iv) passing the squeeze dried paper of step (iii) over heated direct contact drum dryers to obtain a dry latex i impregnated paper;

(v) runni ng the paper from step ( i v) i nto a paper crepi ng unit to obtai n a I atex impregnated creped paper;

(vi) printing a mark on a first side of the paper of step (v);

(vii) coating a release coat on said printed first side of the paper of step (vi);

(viii) passing the paper of step (vii) through a Gravure roll coating system and a Myer bar metering system thereby coati ng the second side of the paper of step (vi i) with an adhesive;

(ix) passing the paper of step (viii) through a drying tunnel;

(x) winding the paper of step (ix) on a rewinding drum; and

(xi ) opti onal ly, cutti ng the paper to a desi red wi dth;

wherein steps (i) ^" (x) are conducted in a single pass.

In one embodiment, the i ntegrated process described herein reduces overall waste by up to 10% based on starting material when compared to manufacturing wherein modules comprising the steps described above are operated separately. In some embodiments, the process is substantially water based. In some embodiments of the process, the aqueous solution of latex comprises naturally occurring latex or synthetic latex. In some embodiments of the process, the heated direct contact drum dryers in step (iv) are heated by circulation of hot water. In some embodiments of the process, the drying tunnel is heated by circulation of hot water. In some embodiments, the process is conducted using solar energy. In other embodiments the process is conducted by using electricity from a power grid.

BRIE F DE SC RIPTION OF AC COM PANY ING DRAWINGS

Figure 1 is a schematic representation of the integrated system described herein.

F igure 2 is a schemati c representati on of the process descri bed herei n.

Figure 3 is a detailed schematic for the adhesive coating process at stage 7 of Figure 1.

DETAIL E D DE SC RIPTION OF T H E INV E NTION

All materials used herein were commercially purchased as described herein or prepared from commercially purchased materials as described herein. Paper based pressure sensitive adhesive tapes are used i n a wi de range of i ndustri es. S ome non-limiting examples include masking tapes used during paint applications; electrical tapes used for temporary masking of components in industries such as the automobile industry; pressure sensitive paper based tapes used for packaging; sports tapes used by athletes; floor marking tapes used on factory floors, and sterile or therapeutic tapes used by medical professionals.

The manufacture of paper based pressure sensitive adhesive tapes requires multiple steps which are typically conducted at different sites. If all the steps could be conducted at a single location, it would result in cost savings.

Accordingly, provided herein are systems and processes which are integrated so as to combine all the previously known modular processes into a system which can be located at just one site. Advantageously, the system and process described herein reduce the overall industrial waste. Typically there are four stages in production of paper-based adhesive tapes - (i) saturation coating and creping of paper; (ii) printing of a mark on a first side of the paper obtained from the first stage; (iii) coating of the printed first side of the paper with a release coating; and (iv) coating of the second side of the paper with a pressure sensitive adhesive. Each of the aforementioned four stages of production (modules) typically causes about 3% waste based on the starting material, so that the overall waste is about 12% based on the starting material. By contrast, in the system and process described herein, all four stages are conducted in a single pass, and the overall waste is reduced to about 3% based on the starting material. A further advantage of the system and process described herein is that they are substantially water based (i.e., substantially free of the use of organic solvents) which also reduces waste and allows for environmentally friendly production. In addition the system described herein can be operated on solar energy because the system uses hot water for heating and drying and said hot water, which is circulated, can be obtained using solar panels.

As used herein, an ^'integrated_, system is a system which combines several stages (modules) of production into a linear single pass production path. The integrated system described herein allows for carrying out multiple steps in the same pass and thereby reduces overall waste based on starting material. As used herein, ^'printing a mark_ on paper refers to printing or embossing one or more than one identifying mark(s) on the paper, where an identifying mark may be a logo, a trade name, a trade mark, a brand name and the like.

As used herein, ^'substantially water based_ system or process refers to a system or process wherein the main solvent used is water, i.e., the system uses less than about 5% or less than about 3% of organic solvents.

As used herein ^'Gravure roll coating system and a Myer bar metering system_, refers to the diagram of Figure 3. The paper is shown as black arrows. The Gravure roll coating system and Myer bar metering system comprises a pick up roller for the paper, a rubber pressure roller, a stainless steel tray for holding adhesive and a stainless steel wire wound a rod which is called the "Myer bar or rod". The pick-up roller is rolled in the adhesive tray and picks up the adhesive from the tray at the bottom The picked adhesive is then transferred or coated on to the paper (or the web) which is passed in between the pick-up roller and the rubber pressure roller. The gap (or the nip) between the pick-up roller and the rubber pressure roller allows for application of the adhesive on the paper with a controlled quantity of adhesive. At this point of time, the stainless steel wire wound rod or Myer bar, is brought in close contact with the adhesive coated paper. This rod is used to remove any excessive adhesive from the paper. The quantity of the residual adhesive on the paper depends upon the diameter of the stainless steel wire which is wound on the rod. This process of removing excess adhesive is also referred to as ^'metering of the adhesive with a Myer rod _.

As used herein, a ^'rewind station_, refers to an apparatus which takes the adhesive-coated and dried paper of the final step and spools the processed paper over a drum to obtain a roll of a paper-based pressure sensitive adhesive tape.

As used herein, a ^'first side_ of a paper is a first surface of the paper which is treated in accord with the processes descri bed herei n. A ^'second si de_ of the paper is the opposite surface, or the surface different from the fi rst side. By ^'single pass_ is meant a unified process where an untreated roll of paper can be taken through four coating steps, namely latex coating, printing (ink coating), release film coating, and adhesive coating in a linear sequence without any transportation or separation of intermediate products.

Referring to Figure 1, the first sequence 1 is unwinding of a roll of paper. The paper is depicted as a solid black line. The paper may have any width up to about 1 meter. The next sequence 2 shows the unwound paper being pulled through a solution of latex to saturate the paper with the latex solution and then squeezing of the paper between rollers. The third sequence 3 shows heated direct contact drum dryers for drying the squeezed latex coated paper. The paper passes over and between the heated drums rotating in opposite directions. The drums are kept at a temperature of about 95 °C to about 100 °C by the action of circulating hot water/steam The next sequence 4 shows creping of the dried paper. Sequence 5 shows printing of identifying characteristics on a first side (or back side) of the paper. The paper is passed over a series of rollers while the ink is blow dried / air dried. Next the same first side (back side) of the paper is coated with a release coating as shown in sequence 6. The printed paper with a release coating thereon is subjected to sequence 7, where the second side (or front side) of the paper is coated with an adhesive using a Gravure roll coating system and a Myer bar metering system. The adhesive coated paper is passed through a drying tunnel 8 which is heated by circulating hot water moving in coils wound around the tunnel. The paper is aligned at station 9 and passes to the rewinding station 10 for winding. Optionally, the meter wide paper / rolls of paper are further cut to size (e.g. to provide 1 inch or 2 inch wide tapes). F igure 2 further delineates the process steps of the system outlined in F igure 1. Thus a single pass may yield several different rolls of desired widths in a final product Optionally, the length of the tape is vari ed by usi ng additi onal rewi ndi ng steps / stati ons.

By "tape" is herein understood an elongated body having a length dimension, a width dimension and a thickness dimension, wherein the length dimension of the tape is at least about the same as its width dimension but preferably greater than its width dimension, and wherein said length dimension is much greater than its thickness dimension. Preferably, the term tape also comprises the embodiments of a ribbon, a strip, a film and may have a continuous or a discontinuous length with a regular or an irregular cross-section. Preferably, the width dimension of the tape is much greater than its thickness dimension. Preferably, the ratio of width to thickness is at least 10, more preferably at least 50, even more preferably at least 100, and most preferably at least 500. By width is herein understood the largest dimension between two points on the perimeter of a cross-section of the tape, said cross-section being orthogonal to the length of the tape. By thickness is herein understood a distance between two points on the perimeter of said cross-section, said distance being perpendicular on the width of the tape. The width and the thickness of a tape can be measured according to known methods in the art, e.g. with the help of a rul er and a mi croscope or a mi crometer, respectively. T he I ength di mensi on of a tape may vary from a few feet to meters.

By "adhesive" is meant herein a substance capable of holding two materials together by surface treatment. As used herein, ^'pressure sensitive adhesives_ are adhesive compositions that have the ability at, or at about, room temperature to sufficiently wet a substrate under gentle pressure and to form a useful bond. As used here, the term ^'useful bond_ differs depending on the substrate application and refers to a corresponding balance of adhesive and cohesive strength. ^'Pressure sensitive adhesives" are normally tacky at room temperature (e.g. at a temperature of at least 15 and at most 30eC) and firmly adhere to a wide variety of dissimilar surfaces upon mere contact without the need for more than finger or hand pressure, thus without the need of applying heat to said adhesive or increasing its application temperature and thus without the need of applying said adhesive in molten state to surfaces. The latex solution used in the system and process described herein may comprise natural latex obtained from rubber trees, or synthetic latex such as neoprene latex or nitrile latex. Any concentration of latex may be used, with a typical concentration of latex in the solution ranging from about 50% to about 55% by weight of the solution.

The release coating may comprise one or more than one non-si I i cone coatings. Non- limiting examples include polyvinyl octadecyl carbamate dispersions (used, e.g., in manufacture of adhesive labels, films, tapes), polysaccharide solutions/emulsions of modified starches (used e.g., in manufacture of writeable / inkjet printable paper), acrylic polymer emulsions (used, e.g., in manufacture of tapes and labels), and aliphatic modified polyurethane aqueous dispersions (used e.g., in manufacture of controlled release of adhesive properties). In one embodiment, the release coatings comprise aqueous emulsions of acrylic polymers. The release coatings are substantially solvent free and are water borne / water based in the systems and processes described herein. The adhesive coating may comprise one or more than one pressure sensitive adhesives. Pressure sensitive adhesives are usually based on an elastomer compounded with a suitable tackifier (e.g., a rosin ester). The elastomers can be based on acrylics, which can have sufficient tack on their own and do not require a tackifier.; bio-based acrylates (e.g., a biological -based macromonomer grafted onto a backbone of acrylate so that the resulting pressure sensitive adhesice uses 60% bio-based materials), butyl rubber, ethyl ene-vinyl acetate with high vinyl acetate content, natural rubber, nitriles, silicone rubbers, styrene block copolymers. Styrene copolymer adhesives and rubber-based adhesives have good low-temperature flexibility, high elongation, and high heat resistance. They are frequently used in hot melt adhesive applications, where the composition retains tack even when solidified. Resins associated with endblocks (cumarone-indene, a-methyl styrene, vinyl toluene, aromatic hydrocarbons, etc.) improve adhesion and alter viscosity. Resins associated with midblocks (aliphatic olefins, rosin esters, polyterpenes, terpene phenolics) improve adhesion, processing and pressure-sensitive properties. Addition of plasticizers reduces cost, improves pressure-sensitive tack, decrease melt viscosity, decrease hardness, and improves low-temperature flexibility. The A-B-A structure promotes a phase separation of the polymer, binding together the endblocks, with the central elastic parts acting as cross-links. Also contemplated are adhesives comprising polychloroprenes; styrene- butadiene-styrene used in high-strength pressure sensitive adhesive applications; styrene- ethylene buty I ene- styrene used in low self-adhering non-woven applications; styrene- ethylene propylene and styrene- isoprene-styrene used in low-viscosity high-tack pressure sensitive adhesive applications; and vinyl ether based adhesives. Acrylic polymer suspensions in water are used for a wide variety of formulated adhesives because of their compatibility with inorganic fillers. Also contemplated within the scope of embodiments of the systems and processes presented herein are non-pressure-sensitive formulations. The adhesive coatings are substantially solvent free and are water borne / water based in the systems and processes described herein. N on- limiting examples of industries served by the methods and systems described herein are foam and furniture fabrication, flexible packaging and converting, recreati onal vehi cl e and mari ne markets, and vari ous assembly operati ons for the automotive and truck industries.

EXAM PL E S

In one embodiment, the paper used in the manufacturing process is about 50 micron thick and weighs 40 grams per square meter. The latex coating deposited on the paper is about 8-10 grams per square meter. The release coating deposited on the latex coated creped printed paper is about 0.3-0.4 grams per square meter, and the adhesive coating deposited on the back side of the paper is about 25 -26 grams per square meter. The drying temperature typically ranges from about 75 °C to about 85 °C, or from about 75 °C to about 95 °C, and any coating or drying speed is a minimum of about 25 meters of paper per minute to a maximum of about 50 meters of paper per minutes. Other thicknesses of paper and deposited coatings are contemplated within the scope of embodiments presented herein. Other temperatures and rates of drying / coating are contemplated within the scope of embodiments presented herein.

The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodi ments without departi ng from the pri nci pi es and spi rit of the i nventi on, the scope of which is defined in the appended claims and their equivalents.

Claims

C LAIMS

1. A n i integrated system for manufacture of paper-based adhesive tapes comprisi ng

(i) a first module for saturation coating and creping paper;

( i i ) a second modul e for pri nti ng a mark on a f i rst si de of the paper obtai ned from the first module;

( i v) a fourth modul e for coati ng the second si de of the paper obtai ned from the thi rd modul e with a pressure sensitive adhesive; and

(v) optionally, cutting the paper into desired widths.

2. T he system of clai m 1 , wherei n the manufacturi ng of paper-based adhesive tapes is substantially water based.

3. The system of claim 1, wherein the saturation coating is conducted with an aqueous mixture of latex.

4. The system of claim 3, wherein the latex is naturally occurring latex or synthetic latex.

5. T he system of cl ai m 1 , wherei n the f i rst modul e further compri ses rol I ers for squeez i ng the saturation coated paper

6. The system of claim 5, wherein the first module further comprises heated direct contact drum dryers for dry i ng the squeezed saturati on coated paper.

7. T he system of clai m 6, wherei n the heated di rect contact drum dryers are heated by circulation of hot water.

8. The system of claim 1, wherein the fourth module comprises a Gravure roll coating system and a Myer bar metering system.

9. The system of claim 1, further comprising a drying tunnel and a rewind station.

10. The system of claim 1, wherein the system is operated using solar energy.

11. The system of claim 1 , wherein the system is operated using electricity from a power grid.

12. T he system of clai m 1 , wherei n a si ngl e pass i n the system provi des the latex coati ng and creping, the printing of a mark, the coating of a release coat, and the adhesive coating to provide a paper-based adhesive tape product

13. A n i ntegrated process for manufacture of paper based adhesive tapes comprisi ng:

(i) initiating the unwinding of a roll of paper which is placed on a drum;

(iv) passing the squeeze dried paper of step (iii) over heated direct contact drum dryers to obtain a dry latex impregnated paper;

(vi) printing a mark on a first side of the paper of step (v);

(vii) coating a release coat on said printed first side of the paper of step (vi); (viii) passing the paper of step (vii) through a Gravure roll coating system and a Myer bar metering system thereby coating the second side of the paper of step (vii) with an adhesive;

(ix) passing the paper of step (viii) through a drying tunnel;

(x) wi ndi ng the paper of step (ix) on a rewi ndi ng drum; and

(xi ) opti onal ly, cutti ng the paper to a desi red wi dth;

wherein steps (i) ^" (x) are conducted in a single pass.

14. The process of claim 13, wherein the process is substantially water based.

15. The process of claim 13, wherein the aqueous solution of latex comprises naturally occurri ng latex or synthetic latex.

16. The process of claim 13, wherein the heated direct contact drum dryers in step (iv) are heated by circulation of hot water.

17. The process of claim 13, wherein the drying tunnel is heated by circulation of hot water.

18. T he system of clai m 13, wherei n the process is conducted usi ng solar energy.

19. The system of claim 13, wherein the process is conducted by using electricity from a power grid.