WO2002092911A1

WO2002092911A1 - Paper or paperboard comprising thermal control material

Info

Publication number: WO2002092911A1
Application number: PCT/GB2002/002025
Authority: WO
Inventors: Edward John Welland; George Andrew Casper; Garret Walter Fortin
Original assignee: Texon Uk Limited; Texon Materiales, S.L.
Priority date: 2001-05-11
Filing date: 2002-05-02
Publication date: 2002-11-21

Abstract

A paper or paperboard material comprising a means for temperature modification, for use in footwear and in packaging, the material comprising a wet-laid short fibre composite material having a plurality of microencapsulated thermal control means being capable of absorbing and desorbing heat by changing phase from liquid to solid and vice versa.

Description

PAPER OR PAPERBOARD COMPRISING THERMAL CONTROL MATERIAL

Field of the Invention

This invention relates to a paper or paperboard material comprising a means for temperature modification, and more particularly to a paper or paperboard material comprising means for temperature modification for use in footwear and in packaging.

Background to the Invention

The use of microencapsulated phase change material (hereafter referred to as "MPCM") to aid thermal comfort of the human body and to modify or control the temperature of other systems is known. Incorporation of the MPCM in various materials by various methods is known, for example the dispersion of MPCM in polymer foams is marketed by Frisby Technologies Inc. Fabrics coated with or impregnated with MPCM in a polymer binder are known. PCT application number PCT/US01/41497 to Freudenberg et al discloses non-woven shoe insole and lining materials containing MPCM for maintaining the thermal climate in an enclosed shoe. According to the present invention there is provided a paper or paperboard material having enhanced reversible and repeatable thermal storage properties comprising: a wet-laid composite of fibrous materials having short lengths; and a plurality of microencapsulated thermal control means in said wet-laid composite, the thermal control means being capable, by absorbing and desorbing heat, of controlling or modifying the temperature of the material or the temperature of an article in close proximity to the composite, wherein the absorption and desorbtion is provided by microencapsulated phase change material changing phase from a solid to a liquid and vice versa.

Description of the Invention

The invention results from the discovery that MPCM can be dispersed in the slurries of fibrous material and water commonly used to create paper and board type materials by the wet-laid process. The wet-laid material containing MPCM can be used for thermal control in many different applications, for example wet-laid cellulose insoles containing MPCM can be used in footwear to aid in management of the thermal environment of the foot in the footwear. Papers and cardboard materials commonly used for packaging could be created, which allow the packaging to play an active part in controlling the temperature of the goods it contains.

The thermal control paper or paperboard material comprises a mixture of short (<30mm) fibres (up to 30 decitex), which may be naturally occurring cellulosic materials such as wood pulp, cotton, or linen or may be synthetic materials such as viscose, rayon, polyester, nylon, polyethylene, polypropylene, acrylic with a polymer binder, MPCM, other water soluble additives such as starch and other particulate fillers and additives such as mineral fillers and pigments.

The manufacture of the thermal control a paper or paperboard material is carried out by a typical wet-laid process, such as the processes used to make cellulose insole materials, paper or cardboard, a general description of which follows:

Fibrous and particulate materials are added to water with other liquid ingredients such as polymer solutions or dispersions and various pH modifying ingredients and surfactants to aid dispersion, such that a slurry of around 10 to 20% of solids in water is achieved. This slurry is continuously agitated and further diluted to the dilution level required to form a uniform sheet at the required weight per unit area. Typical dilution levels are between 1% and 10% solids. This diluted slurry is poured onto a support mesh moving at a rate dependent upon the solids content of the slurry, the rate of pouring and the required weight per unit area of the finished material. The water in the slurry passes through the mesh, the remaining pulp is supported and carried by the mesh through further processes aimed at removing the remaining water and densifying the material. This is often achieved by a combination of suction, squeezing and heating.

At a certain point during this drying process, and usually, but not necessarily, before the material is fully dried, further binders may be added by saturation or coating, for example with a polymer latex that may or may not contain additives including particulate fillers, MPCM, pigments, waterproofing additives (fluorocarbon or silicone dispersions), anti-static additives (carbon black or humectant compounds) and other polymer solutions and dispersions. The level of dry polymeric binder material applied to the other dry ingredients deposited from slurry can be between 1% and 40%, but preferably between 5% and 25%

The resulting temperature-control paper or paperboard material will consist of a mixture of these kinds of ingredients with MPCM, where the ratio of MPCM to the other dry ingredients can be between 1% and 70%, but preferably between 20% and 60%.

The MPCM being fine particulate material, generally between 5μ and 2000μ and with a density generally lower than 1.0 gramme per cm³, can be incorporated into the paper and board material at several stages during the production process.

With the aid of polymeric materials and retention agents they can be dispersed in the slurry with the fibrous materials in such a way that they are preferentially attracted to the surface of the fibrous materials and remain in the web deposited on the mesh, rather than draining through with the water. MPCM at the higher end of the particle size range are better for addition at this stage, but with careful selection of retention agents and binders, the fine materials can also be deposited during this stage of the process.

The MPCM can also be added during a secondary saturation process, where the partly dried, unconsolidated fibrous web is saturated with a binder that is poured onto the surface and allowed to drain through to saturate the whole structure. The binder used at this stage is often a polymer latex with other particulate or liquid additives, the particulate additives may include the MPCM. For addition during this process, the microcapsules are preferably below 75 μ in diameter. Careful choice of surfactant system and viscosity control is needed to overcome the natural tendency of the MPCM to float in water. Typical solids contents of binders formulated for saturation are between 20% and 50%.

The MPCM can also be incorporated into the sizing binders applied by dipping the consolidated web into a bath of liquid binder and squeezing to retain a known weight of binder within the web. Typical materials used for sizing include polymer latex and starch solutions. The MPCM can be incorporated into the sizing binder in the same way as described for the saturation binder.

A further process for applying the MPCM to the paper or paperboard material is by coating with a water-based binder in which the MPCM have been dispersed in the same manner as described above. Various coating methods are commonly used; for example rotary screen, blade over roll, blade over blanket, blade over air. The binder used for coating is usually of higher viscosity than those used for saturation and sizing. The viscosity is increased by the addition of viscosity modifying agents such as acrylic thickeners, and gel forming materials such as sodium alginate and carboxy methyl cellulose.

A Preferred Embodiment of the Invention by way of Example

An embodiment of the present invention will be described by way of example.

Equal, bone-dry quantities of several pulps, noted for having low density and physical properties suitable for insoles, were blended with water in the lab pulper. The following ingredients were used

Weiεht (ε)

Highly purified southern pine kraft pulp 367

Specialty southern pine kraft pulp 360

Coffer filter 719

J-HP retention aid 357

2% starch solution 3417

MPCM with a melting point of 28.2°C 1367

Alum 85

Sodium alginate 567

PH 6.5 A solution of starch was freshly prepared. MPCM equal to the bone-dry mass of the pulps was added to an aliquot of cooled starch solution. This aliquot was in turn blended into the pulper slurry while under agitation.

The pH was adjusted. A retention aid was added to the slurry. The slurry was poured into the mold and additional retention aid was again used. The resulting slurry was formed into a wet mat, suctioned and wet-pressed. The mat was then bone-dried.

The resulting material had the following properties:

Weight (g/m²) 1106

Gauge (mm) 1.93

Density (g /cm³) 0.57

MPCM level 50%

The melting point of the MPCM was chosen to be close to body skin temperature such that the material could be used to remove excess heat from the body when in contact with the skin surface. The material felt cool to the touch and displayed obvious cooling properties when held against warm skin. The material would be suitable for use as a temperature-control shoe insole.

Claims

Claims:

1. A paper or paperboard material having enhanced reversible and repeatable thermal storage properties comprising: a wet-laid composite of fibrous materials having short lengths; and a plurality of microencapsulated thermal control means in said wet-laid composite, the thermal control means being capable, by absorbing and desorbing heat, of controlling or modifying the temperature of the material or the temperature of an article in close proximity to the composite, wherein the absorption and desorbtion is provided by microencapsulated phase change material changing phase from a solid to a liquid and vice versa.

2. A paper or paperboard material according to claim 1 wherein the microencapsulated thermal control means comprises between 1% and 80% of the total weight of the composite.

3. A paper or paperboard material according to either of the preceding claims wherein the thermal control means comprises microencapsulated phase-change hydrocarbon wax.

4. A paper or paperboard material according to claims 1, 2 or 3 wherein the particle size of the microencapsulated phase-change material is 5 to 2000 microns.

5. A paper or paperboard material according to any of the preceding claims wherein addition of the microencapsulated thermal control means is provided during the formation of a slurry during the manufacturing process of the wet-laid composite.

6. A paper or paperboard material according to any of the preceding claims wherein addition of the microencapsulated thermal control means is provided by saturation of the wet-laid composite.

7. A paper or paperboard material according to any of the preceding claims wherein addition of the microencapsulated thermal control means is provided by coating of the wet-laid composite.

8. A paper or paperboard material according to any of the preceding claims wherein addition of the microencapsulated thermal control means is provided by a converting or off-line coating operation where the manufactured base material is impregnated or coated.