MXPA98001195A - Steam barrier formulations based on lign - Google Patents

Abstract

The invention provides a vapor barrier formulation, suitable for coating and lamination on a paper substrate and comprises organosolvent lignin in a dispersion, mica or latex. The laminated paper product is recylab

Description

STEAM BARRIER FORMULATIONS BASED ON LIGNINE Field of the Invention The invention relates to lignin compositions used in the manufacture of paper laminates.

BACKGROUND OF THE INVENTION Generally speaking, a water vapor barrier is one or more walls of a multi-layered bag or container for shipping, which by itself has a degree of resistance to the passage of water vapor from the surrounding atmosphere. up to the packaged product or that has been coated, impregnated or laminated with a material that gives it such resistance. A water vapor barrier is generally rated by its water vapor transmission rate (WVTR), the WTVR is the water vapor velocity transmitted through the barrier at a given temperature and relative humidity. A water vapor barrier is generally used to protect a product with an affinity for moisture, which would cause a physical or chemical change in the product, resulting in a useless product.

Paper is widely used in a variety of commercial and mechanical applications such as in the manufacture of flexible packaging, solid fiber cartons REF: 26922 or corrugated. The physical properties of paper and its relatively low cost are important considerations to make paper attractive for a variety of applications.

Certain properties of conventional paper have limited their use in many mechanical applications. For example, conventional paper easily absorbs moisture and has an exceptionally poor moisture resistance. When conventional paper is placed in direct contact with water, or is exposed to the weather, it easily absorbs water from the environment and as a result does not show any resistance to wetting. For many paper products, such exposure to moisture and resulting reduction in wet strength can destroy the utility of the product. Another property of paper that makes it undesirable for certain applications, is its absorption of oils and fats that makes it unsuitable for use in packaging products that contain oil or grease.

To expand the use of paper, the paper has been treated, laminated or coated, or combined with other materials to form an impermeable barrier to meet the requirements of a specific end use. The most common applications of paper with barrier requirements, are applications of multilayer shipping bags, paper wrappings and food packaging that seek resistance to water, moisture, grease, oils, gas and odor.

Multilayer kraft paper, when combined with one or more barrier materials with specific properties, results in a packaging with a balanced cost / performance ratio. The coatings are usually extruded onto the multilayer kraft paper substrate in single or multiple layers. Coatings and film cover an increasing number of available polymers and modified polymers in addition to simple composite films consisting of two or more layers of resins of specific properties. These structured films can be produced by extrusion or lamination of adhesives or by coextrusion.

Films for bags of boarding are often referred to as free or unsupported films. In manufactured bags, however, they appear as a supported film. That is, they are placed by adhesion or thermal lamination. By far, the greatest growth in volume of coatings and plastic film used in multilayer boarding sacks, has been polyethylene, which can be manufactured in a range of densities, with varying strength, flexibility and melting temperature. The factors that mainly contribute are availability, low cost, and its performance as a water vapor barrier, which are the most common barrier requirements for shipping sacks.

Laminated paper is a generic term that covers any combination of at least one layer of paper bonded to one or more layers of paper, plastic film, cellophane, metal laminate or other material. Thus, laminated paper would be, for example, in the range from two flat sheets of kraft paper bonded by starch adhesive, to a complex structure of kraft paper laminated with polyethylene / metal laminate / polyethylene.

Sheet metal / paper laminations consist of kraft paper bonded by an adhesive or rolling agent, usually wax, hot melt, or polyethylene extrusion, to a continuous sheet of metal laminate.

Fat-proof paper, along with glassine paper and vegetable parchment, are a barrier to products that contain grease or oil. The greaseproof paper uses special sulphate or sulfite pulps (kraft) that are "hydrated". The glass paper is made by passing a greaseproof sheet through a series of alternating fibers and steel rollers heated by steam at high pressures and temperatures. In addition to its resistance to grease, the glass paper has good machining, an excellent printing surface and can be easily combined with various films and metal laminates to meet specific packaging requirements. Since the paraffin laminate softens above 49 ° C, the paraffin-laminated glass paper would be unsuitable for direct contact with very hot products in the packaging operation.

The pulp of kraft or sulphate wood is now used instead of cotton fibers in vegetable scrolls. Unglued, bleached, uncharged and free of other fillers is used as the base material. The outstanding characteristics of vegetable scrolls for packaging purposes are their combination of high resistance to fats and resistance to wetting. The normal grades resist the penetration of almost any type of oils, greases, terpentines, etc., and retain a high percentage of their resistance when wet. Due to its inherent property of poor dry strength, it is difficult to handle it to cover equipment.

Roller wrap commonly refers to the paper used to wrap rolls to prevent them from readsorbing moisture and reverting their shine. In the roller wrap, the most common materials used as a moisture and vapor barrier are petroleum based products such as polyethylene, polypropylene or paraffin. These products have excellent moisture and vapor barrier properties, can be applied economically and have been widely used in the industry. Roll wrapping paper is typically made with two layers of laminated linerboard together with paraffin or polyethylene.

While plastic films and roll wrap paper have good barrier properties, they are not recyclable on paper since the barrier material (polyethylene, polypropylene or paraffin) contaminates the final product and cause problems of operation in sieving or other paper making equipment. Therefore, the roller wrap should be carefully separated from the paper recycling system and sent to landfill after use. The cost of sending to landfill is spiking due to the decreasing availability of filling sites.

As an alternative to landfill disposal, incineration and composting have found application, with composting being more popular than incineration due in part to environmental concerns about incineration in relation to air emissions and ash toxicity. Composting has been gaining popularity as long as the material to be composted has the proper ratio of carbon to nitrogen of 25 to 30 carbons per nitrogen.

The recyclability of vapor and moisture barrier casings has become a major concern as space for landfills is becoming less available and the cost involved with recycling has become prohibitive. Therefore, there is a need to make ground wrap more compatible with typical paper recycling processes by changing the coating or vapor barrier laminate and moisture.

By means of the methods of the present invention, environmentally friendly lignin-based formulations suitable for lamination are provided. The formulations are water based, meet vapor barrier specifications and performance requirements for packaging products, and promote recyclability compared to the current industry standard. Organosolvent lignin with its hydrophobic nature is a good candidate for the formulations of this invention.

Brief Description of the Invention It is an object of this invention to provide vapor barrier formulations. The formulations comprise an organosolvent, mica and latex lignin. In one embodiment, the lignin can be comprised in a dispersion of ammonia and in another embodiment, the lignin can be comprised in a polyacrylate dispersion. The formulations of this invention can be coated and laminated onto a paper substrate to produce a laminated paper product that can be recycled.

Other features and aspects of the invention, as well as other benefits will be inquired from the following more detailed description of the preferred embodiments.

Detailed Description of the Invention The lignin employed in this invention is separated from plant biomass as a small biopolymer by a novel chemical delignification technology based on organic solvents, for example ethanol. Generally referred to as organosolvent lignin, it is a non-toxic, free-flowing powder. It is soluble in aqueous alkalis and in selected organic solvents.

It is generally characterized by its hydrophobicity, high purity, melt flow and a low level of carbohydrates and inorganic contaminants.

The lignin of this invention can be formulated as an aqueous-based water vapor barrier for applications that include, but are not limited to, roll wrap, roll heads, skate wrappers, multilayer bags, cores, corrugated boxes and food packaging. Moreover, the lignin formulations of this invention when laminated onto the appropriate paper substrate produce environmentally friendly end products. The terminal products can be recycled by repulping leaving the lignin in the recycled paper. Alternatively, the lignin can be separated by extraction of the laminate.

Lignin can be formulated as an aqueous dispersion using ammonia. The lignin dispersion is generally obtained by mixing lignin with an ammonia solution such that the final pH of the dispersion is from about 8 to about 12. In order to achieve the proper viscosity, the particle size of the lignin it can be reduced to a final particle size from about 0.1 micron to 20 micron, preferably from about 0.5 micron to about 1.5 micron. The dispersion creates a self-dispersing agent for lignin and the ammonia is a fugitive cation that, when dried, can be removed leaving a hydrophobic lignin in the formulation. Alternatively, other dispersants or dispersing aids may also be used.

The lignin dispersion thus obtained can be mixed with a latex such as, for example, styrene-butadiene rubber, butadiene, vinylidene chloride, neoprene or any other latex which is non-volatile, non-migratory and can reduce the glass transition temperature of lignin. . If a filler is needed, for example, mica, which functions to stabilize the coating dispersion and is believed to be a water vapor barrier, can be added. The ratios are from about 40% to about 60% lignin, up to 33% mica and from about 5% to about 35% latex on a dry weight basis. The lignin formulation thus obtained can be laminated onto an appropriate substrate of paper such as linerboard or kraft paper.

In another embodiment, the lignin can be formulated as an aqueous dispersion using a dispersant that is stable in an acidic system such as polyacrylate. The lignin dispersion is generally obtained by mixing lignin with an aqueous solution of the dispersant such that the final pH of the dispersion is from slightly basic to neutral. In order to achieve the proper viscosity, the particle size of the lignin can be reduced to a final particle size from about 0.5 to about 5 microns.

The polyacrylate lignin dispersion thus obtained, it can be mixed with a latex such as for example polyvinyl acetate or any other latex that is non-volatile, non-migratory, has good adhesive properties and reduces the vitreous transition temperature of lignin. If there is a need for a filler, mica can be added which works to stabilize the coating dispersion and is believed to increase the water vapor barrier. The ratios are from about 5% to about 40% lignin, up to 20% mica and from about 40% to about 60% latex on a dry basis in weight.

The lignin formulations of this invention can be applied as a coating to an appropriate substrate of paper such as kraft paper or linerboard. Any suitable technique such as a Meyer rod coater or front roller may be used.

The coated substrates can then be laminated to a coating weight from 40 to 60 g / m2. The type of latex used as a binder in the formulation will determine the rolling process to be used. Then, if the latex reduces the vitreous transition temperature of the lignin but does not have cold adhesive properties, the coating will need to be dried and then laminated using heat and pressure. If the latex has good adhesive properties, the coating does not need to be dried to the same degree as in the previous case and the lamination will not require heat or pressure. The laminates of this invention can provide a WTVR from about 4 to about 600 g / m2 / day.

The paper laminates of this invention can be recycled by suspending them with an inorganic bse such as for example sodium hydroxide, ammonium hydroxide or a high alkali carbonate at a pH from about 10 to about 12. The suspension is mixed under typical pulp-forming conditions such that the laminate is broken into individual cellulose fibers and an alkaline lignin solution. The suspension is filtered over for example a drum filter or filter press to separate a solution from the lignin and a fiber mat used to make paper. The filtrate can be acidified to a pH from about 4 to about 6 to recover the lignin. Alternatively, the rolled product can again be pulped under neutral conditions leaving the lignin in the fiber. Since this type of approach leads to some type of speckled recycled paper, the obtained fiber is more compatible for use in inner layers of a multilayer paper product where the specifications are not perceptible. In contrast, papers containing paraffin and polyethylene can not yet be used as filler fiber in the inner layers as they migrate or exude towards the surface of the paper in the drier section of the paper machine, causing operational problems. Therefore, paraffin or polyethylene laminates are sent to fill or are currently burned.

Example 1 A lignin dispersion was prepared by mixing 45% lignin in an ammonia solution such that the pH was 10. To reduce the particle size, the lignin dispersion was passed through a horizontal mill of Premier Mili Corporation called Supermill. The particle size was reduced from 10% below 1 miera to 87% less than one miera in diameter.

Example 2 The lignin dispersion of Example 1 was incorporated into a coating formulation as shown in Table 1.

Component (%) by weight Lignin 27.45 Filling 14.10 Latex 8.30 Rheology Modifier 0.15 Water 50 The final Brookfield viscosity measured at 25 ° C and 100 rpm was around 2000 cps. The final solids content was around 50% and the pH was around 8.

Example 3 A lignin dispersion was prepared by mixing 45% lignin in a polyacrylate solution such that the pH was from 6 to 7. To reduce the particle size, the lignin dispersion was treated as in Example 1.

Example 4 The lignin dispersion of Example 3 was incorporated as shown in Table 2.

Table 2 Component (%) by weight Lignin 20.30 Filler 8.70 Latex 28.71 Dispersant 0.29 Water 42.0 The final Brookfield viscosity measured at 25 ° C and 100 rpm was around 2500 cps. The final solids content was around 58% and the pH was around 6.5.

Example 5 The formulation of Example 2 was applied on a base material at a network speed of 30 M / min until reaching a target moisture of 5% and a laminated layer weight of 44 to 54 g / m. Three different base materails were coated: 11.8 kg lining cardboard, 22.7 kg kraft bag and 27.2 kg free sheet netting material. The results of the WVTR measurements indicate an average WVTR of 7.3 g / m / day for a coating weight of 44.5 g / m at a temperature of 25 ° C and 50% RH. The measurements were made in a Permatran-W 3/31 MOCO.

Example 6 The formulation of Example 4 was applied on a lining board base material at a frame rate of 400 M / min to achieve a target laminate weight of 40 to 48 g / m2 and a moisture content of 8 to 10. %. The results of the WVTR measurements indicate an average WVTR of 483 g / m / day for a layer weight of 43.9 g / m2 at 40 ° C and 100% RH. The measurements were made in a Permatran-W 3/31 MOCON.

Example 7 Seven rollers were wrapped with the coated lignin wrapper of Example 6, together with seven control rollers with paraffin wrap (2 wrap wrap). No difference was observed between the wrapped station and the folded station. A strong envelope was observed on the rollers wrapped with lignin which is attributed to the slightly higher moisture content of the roller wrap.

The rollers were divided into two groups. A group of 8 rollers (4 paraffin + 4 lignin) were stored at 25 ° C and 56% RH, and the other group was stored at 37 ° C and 40% RH, to simulate the storage condition at warm temperature. The paper samples were taken from the roller at intervals of 1.27 cms to a depth of 3.81 cms. The samples were analyzed for any change in moisture and brightness during 32 days of storage.

No significant differences in paper gloss and moisture change were observed for the wrapped rolls with the paraffin-coated wrapper or wrapped with the organosolvent lignin-based formulation. As shown in Table 3, the magnitude of the change is small and is considered within the normal variability of the coated paper or the measurement itself.

Table 3 Brightness (ISO) Humidity (%) Envelope with Initial Paraffin 74.2 4.52 Final 74.3 4.65 (25 ° C, 56% RH) Final 73.7 4.65 (37 ° C, 40% RH) Initial Lignin Wrap 74.1 4.41 Final 74.0 4.6 (25 ° C, 56% RH) Final 73.9 4.6 (37 ° C, 40% RH) Example 8 In this example, the laminates of Example 6 were recieled by re-pulping with water at a pH of 7.5 to 4.5% consistency and using a high-speed 200 HP pulper.

The paper coated with repulped lignin contained larger flakes of the dark-colored lignin coating. This equipment was used in a 50:50 ratio with old newspapers such as fiber for the middle layers (layers 2 through 5) in a six-layer chipboard product. This was manufactured in a Kobayashi Ultra-Former six-cylinder, maximum width of 130", 100 M / min to make a multi-pack chipboard with a base weight of 720 g / m2, 5.5% moisture and a thickness of 500 microns The chipped cardboard obtained was of a quality as good as that of the product obtained when only old newspapers were used There was no evidence of the migration of lignin from the inner layers to the surface No ripple or other dimensional oak effect was observed .

In conclusion, the paper coated with lignin has proven to be possible to be formed into pulp again. If specifications for the presence of lignin are questionable on recycled paper, the use of lignin-containing equipment can be limited to applications such as chipped cardboard where it can be added in the middle layers to hide the presence of visible lignin specifications.

The invention and many of its additional advantages will be understood from the above description and it will be apparent that various modifications and changes can be made without departing from the spirit and scope of the invention or sacrificing all its material advantages, the specific materials, procedures and examples hitherto described being merely preferred embodiments.

It is noted that in relation to this date the best method known by the applicant to carry out the invention is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property

Claims (18)

1. A vapor barrier formulation suitable for lamination on a paper substrate, characterized in that it comprises from about 40% to about 60% organosolvent lignin, up to 33% mica and from about 5% to about 35% latex on a dry basis in weight.

2. The formulation according to claim 1, characterized in that the lignin is comprised in a dispersion of ammonia.

3. The formulation according to claim 2, characterized in that the particle size of the lignin is from about 0.1 to about 20 microns.

4. A vapor barrier formulation suitable for lamination on a paper substrate comprising from about 5% to about 40% organosolvent lignin, up to 33% mica and from about 5% to about 35% latex on a Dry base in weight.

5. The formulation according to claim 4, characterized in that the lignin is comprised in a polyacrylate dispersion.

6. The formulation according to claim 5, characterized in that the lignin is from about 0.5 to about 5 microns.

7. A recyclable paper laminate characterized in that it comprises a paper substrate and a coating comprising a vapor barrier formulation comprising from about 40% to about 60% organosolvent lignin, up to 33% mica and from about 5% up to about 35% latex on a dry basis by weight.

8. The laminate according to claim 7, characterized in that the lignin is comprised in a dispersion of ammonia.

9. The laminate according to claim 8, characterized in that the particle size of the lignin is from about 0.1 to about 20 microns.

10. A laminate of recyclable paper characterized in that it comprises a paper substrate and a coating comprising a vapor barrier formulation comprising from about 5% to about 40% organosolvent lignin, up to 33% mica and from about 5% up to about 35% latex on a dry basis by weight.

11. The laminate according to claim 10, characterized in that the lignin is comprised in a polyacrylate dispersion.

12. The laminate according to claim 11, characterized in that the particle size is from about 0.5 to about 5 microns.

13. A method for making a paper laminate having vapor barrier properties, the method characterized in that it comprises the steps of: combined in a formulation from about 40% to about 60% organosolvent lignin, up to 33% mica and from about 5% to about 35% latex on a dry basis by weight; applying the formulation on a paper substrate to produce a coating having a layer weight from about 40 to about 60 g / m2; and laminate the coating.

14. The method according to claim 13, characterized in that the lignin is comprised in a dispersion of ammonia.

15. The method according to claim 14, characterized in that the particle size of the lignin is from about 0.1 to about 20 microns.

16. A method for making a paper laminate having vapor barrier properties, the method characterized in that it comprises the steps of: combined in a formulation from about 5% to about 40% organosolvent lignin, up to 33% mica and from about 5% to about 35% latex on a dry basis by weight; applying the formulation on a paper substrate to produce a coating having a layer weight from about 40 to about 60 g / m2; Y laminate the coating

17. The method according to claim 16, characterized in that the lignin is comprised in a polyacrylate dispersion.

18. The method according to claim 17, characterized in that the particle size of the lignin is from about 0.5 to about 5 microns.