ES2431292T3 - Hot melt adhesive with low application temperature for cigarette manufacturing - Google Patents

Abstract

Cigarette filter comprising a hot melt adhesive based on ethylene copolymer, which can be applied at temperatures between 93 and 149ºC, where the adhesive, comprising vinyl acetate and ethylene, consists of 5 to 45% by weight of vinyl acetate with a melt index of at least 400 dg/min.

Description

Hot melt adhesive with low application temperature for cigarette manufacturing

Foundation of the invention

The present invention relates to the use of a hot melt adhesive that is applied at a low temperature to manufacture cigarette filters. In particular, the hot melt adhesives of the present invention are used to attach the seam that surrounds the filter and to anchor the filter element in situ to the rod.

A cigarette with a tip or nozzle based on a standard filter is manufactured following three distinct stages: (1) manufacture of the filter or cap, (2) manufacture of the rod, and (3) placement of the tip.

The cigarette rod consists of a flow or stream of tobacco wrapped by a paper tube, where the paper tube is glued by a line of suitable adhesive. This procedure takes place at speeds ranging from 2000 to 16,000 cigarettes per minute. The weight of the cigarette rod, the diameter and the length are accurately controlled for a control of the price and the tax aspect.

The manufacturing process of the filter is similar in many ways to the manufacture of the rod, but the materials and manufacturing equipment used are different. Tobacco smoking filters are often made from a curled bast of cellulose acetate fibers. The bast is then heated and rolled to make material about 9 "wide, which contains a homogeneous distribution of fibers. The bast is "treated" in the manner known to separate the fibers, and in a solvent with a high boiling temperature, which is usually known as "plasticizer". Triacetin is applied, for example, by spraying or with the help of a wick. The treated bast is given a cylindrical shape and wrapped with paper. Over a period of time, which can be accelerated by heating, the plasticizer initially partially dissolves the surface of the fibers causing them to become sticky and bond with each other at various points of contact. The plasticizer then migrates into the fiber leaving the surface dry, but the fibers are held together.

The treated bast is shaped like a tube and wrapped in a paper to which glue or an adhesive is added along its entire longitudinal axis. Before the paper comes into contact with the material of the bast, adhesive is applied to the center and the edge, thereby forming the anchor and the seam. During this process, heating rods are used to extend the time in which the adhesive joins the tow. The formed filter rod is then passed through cooling plates that fix the adhesive. This procedure must be carried out since the filter is cut immediately into smaller pieces.

In some applications, such as carbon or multi-component filters, a hot melt adhesive is previously applied to the filter paper and then thermally sealed with the filter manufacturing machine.

In conventional manufacture of cigarette filters, a hot melt adhesive applied at 177 ° C (350 ° C) is used for sewing and a second aqueous adhesive is used for anchoring. An aqueous adhesive with triacetin resistance is chosen. Due to the nature of the bast, there is a high degree of radial tension in the glued joint, so that any adhesive used must be able to almost glue the piece almost instantaneously and maintain it during storage and use. This has led to the use of hot melt adhesives, which are characterized by rapid solidification and allow very high speeds.

Hot melt adhesives based on vinyl acetate and ethylene and polyethylene are often used for this filter. They are preferred because they are relatively non-polar and resist the deteriorating effects of triacetin, the most commonly used plasticizer, which sometimes migrates by acting as a solvent for the adhesive and causing the bond or bond to deteriorate.

For example, US Patent 4,326,543 shows filter cigarettes, cigars and other similar products that use non-rolled fibrous filters, which are held by themselves, where the part containing the tobacco is fixed to the fibrous filters by paper. which is specifically coated with a hot melt adhesive. The hot melt adhesives described herein are based on vinyl acetate / ethylene copolymers having a melt index that should not be greater than 20 and preferably is 12 or less than 12.

US Patent 4,173,504 describes tobacco filters that have a uniform hardness and low pressure and that have been prepared using hot melt adhesives based on (1) a copolymer of vinyl acetate and ethylene with a vinyl acetate content of 0.5 18% molar of the total monomers, (2) a saponification product thereof or (3) a mixed polymer of the components of (1) and (2) and polyethylene, which has a total vinyl acetate content and in 0.5% molar or higher vinyl alcohol, based on the total monomer content of the mixed polymer. The components used in these hot melt adhesives have melt indexes of

order of 1-50 and preferably 4-20. In the event that the melt index is less than 1, the mixing capacity of the copolymer with ethylene is impoverished, while if the melt index is greater than 50, a rubber can be created in the corner of the mold and produced a decomposition of the material.

The adhesives mostly commercially available and used in the manufacture of cigarettes are either hot melts that require temperatures of 177 ° C (350 ° F) or aqueous adhesives that provide resistance to triacetin.

However, there are problems associated with the use of conventional melt adhesives, which are applied at elevated temperatures, generally at 177 ° C (350 ° F). These high temperatures increase the risks of the operator in terms of burns and inhalation of residual volatile substances. In addition, high temperatures require more energy, which requires more suitable manufacturing facilities. High temperatures can also cause premature wear on application equipment, i.e. nozzles, hoses and storage tanks.

The present invention uses hot melt adhesives with low application temperature, which can be applied at temperatures of the order of 93 ° C to 149 ° C (200 to 300 ° F). The advantages of using such low temperatures include a reduced number of heating elements that are required in the adhesive container, a reduced number of volatile emissions and the reduced risk of injury as well as less wear on the application equipment. The use of low temperature hot melt adhesives can also eliminate the need to use aqueous and hot melt adhesives, since some of the hot melt adhesives of the present invention exhibit excellent resistance to triacetin. In addition, lower temperatures reduce temperatures in the reactivation section of the machinery and eliminate the need for cooling plates. Additionally, the hot melt adhesives of the present invention have a fast fixation rate, a better cutting capacity and are comparable or better in terms of triacetin resistance than hot melt adhesives at 177 ° C (350 ° F).

SUMMARY OF THE INVENTION

It has been found, in accordance with the present invention, that hot melt adhesives based on low temperature application ethylene copolymers provide unexpected advantages or benefits in the manufacture of cigarette filters.

DESCRIPTION OF THE INVENTION

The present invention is directed to the use of hot melt adhesive compositions, which can be applied at temperatures between 93 ° C to 149 ° C (200 to 300 ° F), in the manufacture of cigarette filters. In particular, the present invention is directed to a process for manufacturing cigarette filters, and to cigarette filters, where a hot melt adhesive based on a low temperature ethylene copolymer is applied to at least one longitudinal edge or surface. of porous and / or non-porous wrapping paper. The adhesives of the present invention are also applied to multi-component filters or to other filters that have been prepared by previously applying the melt to the filter paper and then heating the coated paper in the machine that makes the filters. As used herein, low temperatures range from 93 ° C to 149 ° C (200 ° C and 300 ° F), preferably 115 ° C to 135 ° C (240 ° F to 275 ° F).

The present invention is directed to the process and to the filters for cigarettes, which comprise any melt adhesive that can be applied at temperatures between 93 ° C and 149 ° C (200 to 300 ° F). Suitable adhesives for use herein include melt adhesives prepared from copolymers of vinyl acetate and ethylene comprising 5 to 45% by weight of vinyl acetate with a melt index of at least 400 g / min. .

I. Melt adhesives based on vinyl acetate and ethylene

The copolymers of vinyl acetate and ethylene (EVA) used herein are those containing at least 15 to 45% by weight of vinyl acetate and having a melt index of at least 400 dg / min. The EVA copolymers preferably comprise less than 40% by weight vinyl acetate (VA), more preferably 28% VA. Preferred copolymers are available from Exxon under the trade name UL 7710 and comprise approximately 28% by weight of vinyl acetate and have a melt index of about 400 dg / min. The amount of copolymer present in the adhesive varies between 5 and 45% by weight, preferably between 10 and 40% by weight.

Mixtures of vinyl acetate copolymers can be used as long as the resulting mixture is within the described ranges of percentages by weight of vinyl acetate and melt index. Therefore it is possible to mix two vinyl and ethylene acetates that have different melt indexes and different percentages of

vinyl acetate These copolymers are useful in the range of 20 to 50% by weight in the adhesive, preferably between 25 and 40% by weight.

In addition to the components described above, the adhesive compositions of the present invention may optionally comprise a second EVA copolymer, in particular one containing approximately 28% by weight of vinyl acetate and having a melt index of 6 to 40 dg / min Preferred copolymers are marketed by Exxon under the name ESCORENE UL 7740 and contain approximately 28% by weight vinyl acetate and have a melt index of approximately 40 dg / min. The amount of this copolymer present in the adhesive varies between 1 and 25% by weight, preferably between 5 and 20% by weight.

The present invention also contemplates the addition of an adhesive chosen from the group consisting of polymers of methyl acrylate and ethylene containing 10 to 28% by weight of methyl acrylate, copolymers of acrylic acid and ethylene having an acid number of 25 to 150, copolymers of methyl methacrylate, polyethylene, polypropylene, polymers of poly (butene-1-co-ethylene) and copolymers of low molecular weight and / or of n-butyl acrylate and low melt index ethylene. When said additive is present, it is present in amounts of up to 15% by weight of the composition.

The adhesives of the present invention also preferably contain a stabilizer or antioxidant. Applicable stabilizers or antioxidants include those mentioned above related to adhesives based on copolymer of n-butyl acrylate and ethylene.

The adhesives may optionally comprise an organic phosphoric acid ester from the group consisting of tricresyl phosphate, triisopropylphenyl phosphate, tributyl phosphate, triethyl phosphate, trimethyl phosphate, trioctyl phosphate or diphenyl phosphate.

The adhesive based on vinyl acetate and ethylene also comprises adherent agents and waxes. The bonding agents and waxes are the same as those described above, for use with adhesives based on copolymers of n-butyl acrylate and ethylene. Preferably the bonding agent is KRYSTALEX® 3085, a low molecular weight thermoplastic hydrocarbon polymer derived largely from alpha-methylstyrenes and having a Ring and Ball softening temperature of 85 ° C and is available from Hercules Inc. The preferred wax is paraffin wax with a melting point of 150 ° C.

Depending on the contemplated end uses of the adhesives, other additives such as plasticizers, pigments and dyes conventionally added to the hot melt adhesives can be added. In addition, small amounts of additional bonding agents and / or waxes such as microcrystalline waxes, hydrogenated castor oil waxes and modified synthetic vinyl acetate waxes, i.e. up to 10% by weight, can also be incorporated formulas of the present invention.

II. Mixes

The present invention also contemplates that the adhesives can be a mixture of poly-alpha-olefins and EVA.

The ethylene / alpha-olefin polymers useful herein are those that have a distribution range of their composition greater than 50% and an Mw / Mn ratio of less than 6. In another configuration, the ethylene / alpha olefin polymers have an index of melting of 40 to 1000 dg / min, a melting point of 71 to 90 ° C, a density of 0.850 to 0.92, a composition distribution index greater than 50% and an Mw / Mn ratio of less than 6. Preferably, ethylene / alpha-olefin polymers have a melt index of 50 to 500 dg / min and a density of 0.885 to 0.90. The ethylene / alpha olefin polymers can be copolymers of ethylene and alpha-olefin, for example, butene.

As used herein, the composition distribution index or the distribution index of the short chain branches refers to the percentage by weight of polymer molecules having a comonomer content within 50% of the total average content. of comonomer.

III. Preferred Settings

The hot melt adhesives of the present application can be applied at relatively low temperatures below 300 ° F and can be used in the present invention, in which an adhesive is applied at a low temperature to at least one longitudinal edge of the porous wrapping paper and / or not porous. One of the preferred configurations of the adhesive is that it contains:

a) 31 parts of paraffin wax with a softening point of 150ºF:

b) 21 parts of vinyl acetate and ethylene copolymer with a melt index of 400 and an ace content

28% vinyl tato;

c) 11 parts of vinyl acetate and ethylene copolymer with a melt index of 43 and an ace content

28% vinyl tato; d) 37 parts of alpha-methylstyrene adherent resins; Y e) 0.5 parts of an antioxidant stabilizer.

The resulting adhesive is characterized by a viscosity of less than about 5 Pas (5000 cps) at 121 ° C, a Ring and Ball softening point or temperature of 80 ° C to 115 ° C, fiber tear bonds in the wrapping paper from -18 ° C to 51 ° C (0ºF to 120ºF).

The following examples are merely examples and are not intended to limit the scope of the present invention.

EXAMPLES

In the following examples, which are shown for illustrative purposes only, all proportions are by weight and all temperatures are in degrees Celsius unless otherwise indicated.

In the examples, all adhesive formulas were prepared in a single-blade mixer that was heated to 135 ° C by mixing the components until a homogeneous mixture was obtained.

The adhesives were then subjected to various tests that simulated the properties necessary for a successful commercial application.

The viscosities of the mixture of hot melt adhesives were determined on a Brookfield RVT Thermosel viscometer using a spindle number 27.

The test samples to determine the shear and exfoliation resistances at an elevated temperature were prepared as follows: an adhesive bed was applied at 121 ° C to a strip of Kraft paper of 50 pounds and about 2.54 cm (1 inch) of wide by 7.62 cm (3 inches) long across the entire width of the paper. A second piece of Kraft paper of the same dimensions was placed just above the first piece and a weight of 200 grams was placed on the base of the compound. The width of the compressed adhesive bed was 1/2 inch.

Exfoliation and shearing at elevated temperature were determined by applying a weight of 100 grams in each sample and placing the samples in a mechanical aspiration oven. The temperature was raised in increments of 5.5 ° C (10 ° F) from 38 ° C and the samples were kept at a certain temperature for 15 minutes for conditioning. The healing cycle ended when the final link failed. Exfoliation and shear samples were prepared and analyzed in duplicate. The high exfoliation and shear value shown is equivalent to the average failure temperature of the two links. In some cases, the sample failed as the temperature was adjusted in increments of 10 ° and what happened was recorded.

Adhesion at various temperatures was determined by applying a sphere of 6.35 cm (1/4 inch) of adhesive width to a piece of 5.08 cm (2 inches) by 7.62 cm (3 inches) of wrapping paper not porous and immediately contacting a second piece of paper. The bond was treated at each temperature for 24 hours. The links were separated manually and the amount of torn fiber (FT) was determined.

Adhesive penetration was measured using a porous wrapping paper. This test is performed to measure the staining of the paper by the adhesive. Six sheets of 5.08 x 2.54 cm (2x1 ”) of wrapping paper were stacked. A 5.35 mm 1/4 "wide bed of adhesive was applied between the two central sheets, and treated at a temperature of 43 ° C (110 ° F) for 24 hours. The penetration of the adhesive into the upper and lower sheet was noted.

Exposure time / fixation time was measured on an automated link meter using a 1 mm (0.04 ”) uncompressed bed applied to 65 lb of corrugated wall. The exposure time measures the amount of time the product can remain in the air, that is, it reaches 100% tear of the fiber, in 10 seconds of compression time. Fixation time is the amount of time required to compress and achieve 100% fiber tear with 1 second of exposure time.

Triacetin resistance was measured after immersing the adhesive bond for 24 hours in triacetin.

EXAMPLE 1

In this example, conventional adhesives were compared with adhesives with a low application temperature corresponding to the present invention. Comparative Examples A and B are conventional adhesives for gluing the wrapping paper that are applied at 177 ° C (350 ° F). Samples 1-4 correspond to the present invention and are applied at 121 ° C (250 ° F). The formulas of the adhesives studied are shown below:

Sample A: is a commercially available EVA hot melt adhesive, which appears under the designation 34-2760 in the National Starch and Chemical Company

Sample B: is a commercially available EVA hot melt adhesive, which appears in the National Starch and 5 Chemical Company under the designation 34-2757.

 Sample 1: Quantity (% by weight)  Phenol hindered (antioxidant) 0.5%  Paraffin wax 150ºF 31

10 SCORENE UL 710 (EVA, MI 400 dg / min, 28% VA) 21 ESCORENE UL 7740 (EVA, MI 40 dg / min, 28% VA) 11 KRISTALEX 3085 (a-methylstyrene, 85ºC) 37

Sample 2: (reference)

15 BHT (antioxidant) 0.5 EPOLENE C10, 104 ° C (polyethylene polymer) 50 ECR 179G (hydrocarbon resin) 40 Microcrystalline wax 195ºF 10

20 Sample 3: (reference) Phenol hindered (antioxidant) 0.5 Paraffin wax 150ºF 31 EXXON XW 23-AH (EnBA, 33% BA, MI 300 dg / min) 21 ELF AUTOCHEM 35BA40 (EnBA, 33% BA, MI 40 dg / min) 11

25 KRISTALEX 3085 (a-methylstyrene, 85 ° C) 37

Sample 4: (reference) Phenol hindered (antioxidant) 0.5  Paraffin wax 150ºF 35

30 Poly-alpha-olefin 30 EASTOTAC H100-R, 100 ° C 35

The results are shown below in table 1:

35 TABLE 1

Sample A *

Sample B * Sample 1 Sample 2 * Sample 3 * Sample 4 *

Viscosity @ Application temperature

-4400 cps -2735 cps -2390 cps -3600 cps -3025 cps -2820 cps

Adhesion @ Application temperature

Temp. amb.

100.50% 100.50% 100% 100% 100% 100%

40th

100% 100% 100% 100% 100% 100%

100º

100% 75.50% 100% 100% 100% 100%

Penetration @ 110ºF

Light Light Very light Very light Light Light

Triacetin resistance 24 hours

0% fiber tear 25% fiber tear 0% fiber tear 80% fiber tear 0% fever tear 0% fiber tear

Exfoliation / Shearing

 Adj 130º / Adj 190ºF Adj 130º / Adj 190ºF 1102º / 150ºF  110º / Adj 190ºF 100º / Adj 150ºF 100º / Adj 150ºF

Stability 260 hours

@ 350ºF @ 350ºF @ 250ºF @ 250ºF @ 250ºF @ 250ºF

Char

Very light Any Any Any Any Any

ER

Any Any Any Any Any Any

Others

Any Yes. Misty Any Any Yes. Separation Any

Delta visc.

-51.0% -24.0% 1.4% 13.3% -0.9% 2.1%

4 ”wide bed @ Application temperature Exposure time with 10 second compression

1.7 s 1.0 s 2.0 s 4.0 s 1.5 s 20 s

Fixing time with exposure time of 1 s

Partial FT = 1.3 s Full FT = 3.3 s Partial FT = 4.0 s Full FT = NA Partial FT = 0.7s Full FT = 2.0s Partial FT = 0.7 s Full FT = 1.1 s Partial FT = 1.5s Full FT = 6.0 s Partial FT = 20s Full FT = 4.3 s

• Reference samples

The results in Table I above indicate that adhesives that are applied at low temperature, samples 1,2,3, and 4, have a good adhesion comparable to conventional adhesives. Samples 1 and 2 have a higher degree of penetration and have good thermal stability. The large change in viscosity observed with samples A and B at 260 hours indicates that these adhesives are not stable; EVA is degrading. Sample 2 exhibits excellent fiber tearing even after 24 hours of exposure to triacetin.

A significant difference between the adhesives of the present invention and the conventional adhesives is that the adhesives of the present invention have a long exposure time and a fast fixation time that allows for rapid drying and fixation before the cutting of the cigarette.

Other configurations of the present invention are the following:

one.

A cigarette filter comprising an ethylene copolymer that is applied at low temperature based on hot melt adhesive, which can be applied at temperatures between 93 ° C and 149 ° C (200 to 300 ° F), such that the adhesive comprises vinyl acetate and ethylene which It consists of 5 to 45% by weight of vinyl acetate with a melt index of at least 400 dg / min.

2.

A cigarette filter according to the configuration which also comprises a second copolymer of vinyl acetate and ethylene, so that the second copolymer of vinyl acetate and ethylene comprises 28% by weight of vinyl acetate with a melt index of 6 to 40 dg / min.

3.

A cigarette filter according to the configuration further comprising a polymeric additive selected from the group consisting of polymers of methyl acrylate and ethylene containing 10 to 28% by weight of copolymers of methyl acrylate, acrylic acid and ethylene, with a acid number of 25 to 150, copolymers of methyl methacrylate, polyethylene, polypropylene, poly (butane-1-co-ethylene) polymers and copolymers of low molecular weight n-butyl acrylate and / or with a melt index low, and combinations thereof.

Four.

A cigarette filter according to configuration 1, in which the adhesive consists of a mixture of poly-alphaolefin and EVA.

5.

A cigarette filter according to configuration 1, in which the hot melt adhesive consists of:

a) 31 parts of paraffin wax with a softening point of 150ºF b) 21 parts of copolymer of vinyl acetate and ethylene with a melt index of 400 and a vinyl acetate content of 28%; c) 11 parts of vinyl acetate and ethylene copolymer with a melt index of 43 and a content of

28% vinyl acetate; d) 37 parts of alpha-methyl styrene adherent resins; Y e) 0.5 parts of antioxidant stabilizer

6.

The process to prepare a cigarette filter that consists of applying a hot melt adhesive based on ethylene copolymer at a temperature between 93 and 149ºC (200 to 300ºF) to porous and / or non-porous wrapping paper, where the adhesive consists of acetate of vinyl and ethylene with 5 to 45% by weight of vinyl acetate and a melt index of at least 400 dg / min.

7.

The process according to configuration 6, where the adhesive consists of a mixture of poly-alpha-olefins and

8.

The process according to configuration 20, where the adhesive consists of:

a) 31 parts of paraffin wax with a softening point of 150ºF b) 21 parts of copolymer of vinyl acetate and ethylene with a melt index of 400 and a content of

28% vinyl acetate; c) 11 parts of vinyl acetate and ethylene copolymer with a melt index of 43 and a content of

28% vinyl acetate; d) 37 parts of alpha-methyl styrene adherent resins; Y e) 0.5 parts of antioxidant stabilizer

Claims (8)

1. Cigarette filter comprising a hot melt adhesive based on ethylene copolymer, which can be 5 applied at temperatures between 93 and 149 ° C, where the adhesive, comprising vinyl acetate and ethylene, consists of 5 to 45% by weight of vinyl acetate with a melt index of at least 400 dg / min. 2. Cigarette filter according to claim 1, further comprising a second copolymer of vinyl acetate and ethylene, in which the second copolymer of vinyl acetate and ethylene consists of 28% by weight of vinyl acetate with a melt index of 6 to 40 dg / min. 3. Cigarette filter according to claim 1, further comprising a polymeric additive selected from the group consisting of polymers of methyl acrylate and ethylene containing 10 to 28% by weight of copolymers of methyl acrylate, acrylic acid and ethylene , with an acid number of 25 to 150, copolymers of me 15 methyl tacrylate, polyethylene, polypropylene, poly (butane-1-co-ethylene) polymers and copolymers of n-butyl acrylate of low molecular weight and / or with a low melt index, and combinations thereof.

Four.

Cigarette filter according to claim 1, wherein the adhesive consists of a mixture of poly-alphaolefin and EVA (copolymer of vinyl acetate and ethylene).

5.

Cigarette filter according to claim 1, wherein the hot melt adhesive consists of:

a) 31 parts of paraffin wax with a softening point of 65.5ºC (150ºF); b) 21 parts of copolymer of vinyl acetate and ethylene with a melt index of 400 and a content of 25% vinyl acetate; c) 11 parts of vinyl acetate and ethylene copolymer with a melt index of 43 and a vinyl acetate content of 28%; d) 37 parts of alpha-methyl styrene adherent resins; and e) 0.5 parts of an antioxidant stabilizer. 6. Method for the manufacture of a cigarette filter, comprising the application of a hot melt adhesive based on ethylene copolymer at a temperature between 93 and 149 ° C (200 and 300 ° F) on paper wrapping the porous and / or non-porous filter , where the vinyl acetate and ethylene adhesive consists of 5 to 45% by weight of vinyl acetate, which has a melt index of at least 400 dg / min.

7.

Process according to claim 6, wherein the adhesive consists of a mixture of poly-alphaolefin and EVA (copolymer of vinyl acetate and ethylene).

8.

Method according to claim 6, wherein the adhesive consists of the following:

a) 31 parts of paraffin wax with a softening point of 65.5ºC (150ºF); b) 21 parts of copolymer of vinyl acetate and ethylene with a melt index of 400 and a content of 28% vinyl acetate; c) 11 parts of vinyl acetate and ethylene copolymer with a melt index of 43 and an ace content 45% 28% vinyl tato; d) 37 parts of alpha-methyl styrene adherent resins; and e) 0.5 parts of an antioxidant stabilizer.