GB2334428A

GB2334428A - Heat or cold insulating insole

Info

Publication number: GB2334428A
Application number: GB9903855A
Authority: GB
Inventors: Sylvain Zanni
Original assignee: CENTRE TECH CUIR CHAUSSURE; Centre Technique Cuir Chaussure Maroquinerie
Current assignee: CENTRE TECH CUIR CHAUSSURE; Centre Technique Cuir Chaussure Maroquinerie
Priority date: 1998-02-23
Filing date: 1999-02-22
Publication date: 1999-08-25
Anticipated expiration: 2019-02-22
Also published as: DE19907314A1; ES2154582A1; ITMI990321A1; GB9903855D0; FR2775331B1; PT102260B; ES2154582B1; PT102260A; GB2334428B; FR2775331A1; IT1308614B1

Abstract

A heat or cold insulating insole comprises at least one core 2 having a three dimensional textile structure, the core being impregnated with at least one phase change material (PCM) 1, wherein the core is positioned within a covering 3 impermeable with respect to the PCM. Typically, the PCM is at a solid-liquid transition and is chosen from polyethylene glycol, paraffins, and hydrated salts. The three dimensional structure may be non-woven and is preferably based on polyester fibres. The covering may be formed from polyvinyl chloride or polyethylene. A process for manufacturing the heat or cold insulating insole comprises the steps of impregnating the three dimensional textile structure by dipping in a bath of a liquid PCM, removing the impregnated structure and allowing it to cool to room temperature so as to obtain the core, and sealing the core within the impermeable covering.

Description

The present invention relates in a general way te beat- or cold-lnslating flexible linings which can be used, for example, in clothing and in particular as an insole for footwear.

In the field of heat- or cold-insulating flexible linings, Patent US 4,331,731 discloses an insole with a pliable and flexible structure which generates heat. According to Figure 2, this sole comprises, in an air-permeable covering (6), on the one hand, a thick plastic sheet (1) in the form of an opencell foam comprising an exothermic agent; this sheet is enclosed in an air-permeable covering (2) which furthermore incorporates a cushion (5) made of opencell plastic foam. The permeability of the covering (6), in contact with the cushion (5), allows the sole to breathe air out and in under the effect of the mechanical stresses of the foot of the user.

Patent US 5,290,904 discloses, according to Figure 2, a layer for protection against heat comprising two layers made of non-flammable flexible material (in particular aluminium) hermetically enclosing a solidified base (of silicone rubber type) which can comprise micro- or macroencapsulated phasechange materials (PCM) of paraffin type.

Published Patent Application WO 97/06803 discloses, according to Figure 3, a sole body comprising an absorbent body (13) composed of two layers. The first layer is composed of an absorbent material (30) which can be impregnated with paraffin and the second layer is composed of a thin copper film (31). This structure makes it possible to immobilize the paraffin in the liquid state and reduces the risk of escape of the paraffin if the partitions (17 and 18), made of rubber, are damaged.

Although there already exist cold- or heatinsulating flexible linings which, because of their specific structure or use, withstand mechanical stresses, it appeared necessary to have available an insole which is simple to manufacture, without encapsulation of the PCM, does not exhibit a problem of deterioration, is convenient at the time of use and is erfesctnvG as a thermal lining.

The present invention intends to solve this problen.

A first subject-matter according to the invention is a heat- or cold-insulating flexible insole which withstands mechanical stresses and which comprises at least one phase-change material (POM), a core, comprising a three-dimensional textile structure impregnated with PCM, and a covering which is impermeable with respect to the PCM, within which covering is positioned the said core.

"Insole" is understood to mean a sole situated immediately below the planta which thus makes it possible to maintain the foot at body temperature, either by protecting it from cold with appropriate PCMs or by protecting it from heat with other appropriate PCMs. Although various insoles have been disclosed by the abovementioned patent applications, workers on road bituminous mixes currently use, unlike the present invention, insoles composed of a textile sheet, of a layer of foam and of a sheet of aluminium.

The term "which withstands mechanical stresses" according to the present invention is understood to mean that the sole, under the effect of repeated or continuous mechanical stresses, for example under the weight of the user, retains its structure and its insulating qualities.

PCM" according to the present invention is understood to mean any material capable of storing thermal energy in the form of latent heat by a phase change. Numerous materials exist which exhibit this property. Mention may be made, for example, of paraffins; hydrated salts, such as CaC12-6H20 ; a mixture of hydrated salts with other compounds; glycols, glycerol, glycosides or mixcures of water with glycols, glycerol or glycosides; or clathrates. The choice of the PCM or PCMs to be used in the flexible lining according to the present invention depends manly G. two factors: the latent heat which can be stored by phase change and the temperature of the phase change. Generally, the greater the latent heat via phase change, the better the material of PCM type, because there is more thermal energy which can be stored by the material. The choice of the transition or phase-change temperature of the PCM depends on the use or destination of the lining according to the invention. Use may be made of PCMs with a solid-solid or solid-liquid phase transition, depending on the transition temperature which it will be desired to obtain. Use may also be made, in the lining according to the invention, of mixcures of PCMs with different transition temperatures.

Textile" according to the present invention is understood to mean natural or chemical, fibrous or filamentary materials, whatever their arrangement or structure, intended for the manufacture of textile articles. The natural materials can be of plant or animal origin. Mention may in particular be made, as material of plant origin, of hemp, cotton, jute, kapok, ramie, sisal or coconut. Mention may in particular be made, as material of animal origin, of wool, silk or the various hairs of sheep, goat, camel, llama, alpaca, vicuna, guanaco, angora rabbit, seal or reindeer. The chemical materials comprise all fibres manufactured by man from starting materials of organic nature, already present in the natural state and which are either converted under the effect of chemical agents, or created by chemical synthesis. Artificial or synthetic fibres distinguished. Mention may be made, as artificial fibres, of regenerated cellulose in particular viscose, man-made staple fibre or cuprammonium, or cellulose esters, in particular cellulose acetate and triacetate. Mention may be made, as synthetci fibres, of acrylic or polyacrylic fibres, polyamideZ polyesters and polyurethanes. The textiles according to the present invention can be either woven or non-woven or alternatively knitted.

The term "impermeable covering" according to tne present invention is understood to mean any covering made of a material which is impermeable with respect to PCMs which makes it possible to isolate the PCM or PCMs from the external environment. This means, in this case, in the present invention, that the PCM or pCMs incorporated in the textile cannot migrate, neither in the solid state nor in the liquid state, towards the external environment. Mention may in particular be made, as impermeable material, of plastics, such as polyethylene and poly(vinyl chloride), or other materials in the film form.

As will be seen in the second subject-matter according to the invention, the process for the manufacture of a flexible insole according to the invention is simple, which allows easy shaping of the linings according to their destination. For this reason , the sole according to the invention can take any shape desired. It can therefore be used for any type of footwear, such as ski, town or work footwear In a preferred embodiment according to the invention, the textile impregnated with at least one PCM is a non-woven.

In a more preferred embodiment, the non-woven textile is based on solid fibres, in particular made of polyester.

In another preferred embodiment according to the invent ion, it is preferable for the PCM to be at solid-liquid transition.

Advantageously, it is preferable for the PCM to be chosen from poly(ethylene glycol) paraffins and hydrated salts.

In a very advantageous way, it is preferable for the PCM to be a paraffin and/or poly(ethylene glycol).

The impermeable covering is advantageously chosen from poly(vinyl chloride) and,Do7vthylene.

The non-woven textile preferably has a thickness of 2 to 6 mm, more preferably of 3 to 5 mm.

It is also preferable for the non-woven textile to be impregnated with 1.8 to 3 eg of Pcm per m2 of textile.

In a preferred embodiment according to the invertion, the sole can comprise a sheet of a textile adhesively bonded to the outer face of the covering in contact with the foot. Textiles which are pleasant and hygienic on contact with the skin, such as textiles based on natural materials, are particularly considered.

A second subject-matter according to the invention is the process for the manufacture of the sole according to the invention, comprising the stages of: - impregnating the three-dimensional textile structure by dipping in a bath of PCM in the liquid form, - taking out the three-dimensional structure impregnated with PCM, - leaving the said three-dimensional structure to cool to room temperature or cooling it under accelerated conditions, in order to obtain the core, - optionally cutting up the said three-dimensional impregnated structure, according to the use chosen, - covering the core with an impermeable material, which is sealed in order to form a covering which is impermeable with respect to the phase-change material.

The textile can be cut up before or after dipping in the bath of PCM, depending on the advantages Which this represents for the manufacturer.

Figure 1 represents a view in perspective of an insole comprising a core 2, comprising a three dimensional textile structure impregnated with the PCM 1, and a covering 3 which is impermeable with respect to the PCM, within which covering is positioned the core.

Figure 2 represents a cross-sectional view IT/IS of Figure 1.

Figure 3 represents an insole according to Figure 2 [sic) with a sheet 4 of a textile cdhesive'y bonded to the outer face of the covering in contact with the foot.

The examples which follow describe an insole according to the invention and make it possible to illustrate the invention. They should in no way be regarded as a limitation of the scope of the protection sought by the appended claims.

Example 1: Process for the laboratory manufacture of an insole for footwear intended for people working on road bituminous mixes.

The PCM must be heated above its melting point in order to be in liquid form.

The textile, which is in non-woven form based on polyester fibres, which has a thickness of S mm and which has been cut up beforehand, is immersed in the bath of PCM (paraffin or PEG, as indicated in Example 2) one or more times, depending on the grammage desired.

After the various immersions, the grammage must be greater than that desired, because the textile must subsequently be lightly squeezed in order to give a good distribution of the PCM and to avoid regicns of excess.

The impregnated textile is left to cool to room te.mterature until the PCM has hardened The impregnated textile piece in the form of an insole is subsequently covered up between two plastic films heat-sealed under vacuum. One of these two films can be laminated beforehand onto an outer sheet of a textile intended to be in contact with the foot.

Example 2: Effectiveness of the insoles manufactured in Example 1.

The temperature limit which the skin endures, in this case in the feet, is 420C. Above this limit, there is a feeling of burning. People who work o road bitz-,inous mixes currently use footwear which comprises an insole composed of a textile sheet, oI a layer of foam and of a sheet of aluminium. With such sole, the workers are obliged to leave their working place after having been there continuously for approximately 30 minutes.

Insoles manufactured as described in Example 1, incorporating paraffins or polytethylene glycol) (PEG), were tested in comparison with the control sole 1 (textile with a thickness of 5 mm not impregnate with PCM) and the control sole 2 (textile, foam and sheet of aluminium), in order to evaluate the duration of presence at their working places of workers on road bituminous mixes. The results are given in Table 1.

The laboratory results of the thermal insulation test, according to Standard EN 344, paragraph 4.3.S.1, give the following duration results (expressed in minutes) according to the temperature of 42cm.

Table 1

Duration (min) Control 1 28.2 Control 2 28.9 1 42.2 2 51.2 3 49.2 4 56.8 1: Sole with a thickness of S mm incorporating 3000 g of paraffin, with a latent heat of 183.9 joules/g, per m2 of textile.

2: Sole with a thickness of 5 mm incorporating 3000 g of paraffin, with a latent heat of 204.3 joules/g, per m2 of textile.

3: Sole with a thickness of 5 mm incorporaing 30coo g of PEG, with a latent heat t of 175.3 jouleszg, per m of textile.

4: Sole with a thickness or 5 mm incorporaing 4600 g of PEG, with a latent heat of 171.1 joules,g, per m2 of textile.

As may be seen, the soles according to the present invention make it possible to multiply by two the time needed to reach 420C.

Example 3: Evaluation on a work site of the insoles.

Starting with the PCM selected, PEG 1500, it is a question of measuring the increase in thermal protection contributed by the PCM under actual wearing conditions, in order to confirm the laboratory results.

The assessment of the results will be twofold since, on the one hand, heat sensors are placed in the items of footwear in order to give information objectively about the true temperature at the surface of the dermis of the foot and, on the other hand, the wearer will indicate his feelings of heat and of comfort.

In order to separate the effects related to the variations in ground temperature from one region to another or in residence time of the wearer on the hot bituminous mix, comparative tests are carried out between the insole comprising the PCM and the "control 2" insole according to Example 2. These components are worn at the same time, on the left foot for one and the right foot for the other.

Two types of test were carried out: - static tests: the wearer remains in a static position on tar freshly deposited i a wheelbarrow until the temperature reaches 420C and then the cooling is observed, items of footwear on the feet, - dynamic tests: the components are worn by a site worker for an entire day while carrying out his job "normally'.

The reference insole is placed ir. the right item of footwear and the insole with POM according to the invention in the left Item of foo-ear. Three thermocouples are placed on t first ones, on the foot side: one sensor at the region of flexion o the foot, the other at the arch of the foot and the third at the heel. A package makes it possible to carry out the recording without bothering the wearer and then to transfer the data to a computer.

RESULTS: - Static tests:

STATIC TEST PCM I REFERENCE Time for rise to 420C 40 Thin 18 min Maximum temperature 43.50C 43.50 C The limit temperature which can be endured by the foot (420C) is reached in 18 minutes with the reference sole (control 2), against 40 minutes for the sole incorporating the POM PEG 1500. The time was more than doubled with the sole according to the invention.

- Dynamic tests

DYNAMIC TEST PCM R2FERrNCE Time for rise to 420C 1 h 50 min 1 h 10 min Maximum temperature 42.8 C 45.8 C Cumulative time above 1 h 18 min 3 h 27 min 420C The results confirm the static tests since the time to reach 420C is greater by 40 minutes with the sole of the invention (PCM).

Furthermore, once the temperature of 420C has been reached, a significant difference in behaviour is observed between the two soles: - the PCM sole according to the invention reaches a maximum temperature of 42.80C, against 45.80C for the reference sole, - the cumulative time above 42:c is 68 sic] minutes for the PCM sole according to the invention, aains 20, minutes for the reference sole, - whereas the temperature of the reference sole is subject to large differences (from 37 to 45.8CC), the temperature of the PCM sole according to the invention is more stable (from 40 to 42.80C).

It has been demonstrated that the insole incorporating the PCM makes it possible to limit the temperature to a threshold of 42 .80C, which remains acceptable by the body.

Furthermore, as regards the regeneration during the meal break, the residence time on the hot tar being the same for both items of footwear, the PCM sole cools more slowly: this is due to the recrystallization of the PCM, which gives off energy.

The slope for rise in temperature after the meal break is markedly lower for the PCM sole, which is reflected by a time for rise to 420C of greater than 12 minutes. This difference shows that the duration of the .eal break has made it possible to cool the PCM sufficiently for it to change state (at least partially) and to again be active.

CONCLUSIONS: The tests on work sites have made it possible to confirm the laboratory results. The PCM sole according to the invention is therefore effective and rakes it possible to slow down the rise in temperature.

The maximum temperatures are also reduced, which makes it possible to avoid temperature peaks which are a source of burn injuries. It is also possible to take advantage of a regeneration of the PCM during the midday break when the PCM sole according to the invention is used.

Claims

CLAIMS 1. Heat- or cold-insulating flexible insole which withstands mechanical stresses and which cmprises at least one phase-change material (?CMj 1 characterized in that it comprises at least one core

2 , comprising a three-dimensional textile structure impregnated with the phase-change material 1 , and a covering 3 which is impermeable with respect to the phase-change material, within which covering is positioned the said core.

2. Sole according to Claim 1, characterized in chat the three-dimensional structure is non-woven, preferably based on solid fibres, in particular made of polyester.

3. Sole according to Claim 1 or 2, characterized in that the phase-change material is at solid-liquid transition.

4. Sole according to Claim 3, characterized in that the phase-change material is chosen from poly(ethylene glycol), paraffins and hydrated salts.

Sole according to Claim 4, characterl'zed in that the phase-change material is a paraffin and/or poly(ethylene glycol).

Sole according to Claim 1, characterized in that the impermeable covering is composed of a material chosen from poly(vinyl chloride) and polyethylene.

Sole according to Claim 2, characterized in treat the non-woven three-dimensional structure exhibits a thickness of 2 to 6 mm, preferably of 3 to S mm.

8. Sole according to Claim 1, characterized in thbt the non-woven three-dimensional structure is impregnaed with 1.8 to 3 kg' of PCM per m2 of textile.

9. Sole according to Claim 1, characterized in that it comprises a sheet 4 of a textile adhesively bonded to the outer face of the covering in contact with the foot.

10. Process for the manufacture of the sole according to Claim 1, comprising the stages of: - impregnating the three-dimensOna textile structure by dipping in a bath of Wb1 in ...e liquid form, - taking out the three-dimensional structure impregnated with POM, - leaving the said three-dimensional structure to cool to room temperature or cooling it under accelerated conditions, in order to obtain the core (2), - optionally cutting up the said impregnated three-dimensional structure, according to the use chosen, - covering the core 2 with an impermeable plastic, which is sealed in order to form the covering which is impermeable with respect to the phase-change material.

11. A heat or cold insulating flexible insole as hereinbefore described.

12. A heat or cold insulating flexible insole as hereinbefore described with reference to the drawings.

13. A process for the manufacture of a sole as hereinbefore described.

14. A process for the manufacture of a sole as hereinbefore described with reference to the drawings.