The invention relates to an element capable of regulating the temperature of the surface with which it is in contact. Advantageously, the element works through the use of materials that synergistically balance (A) evaporative endothermy and (B) thermal inertialization.

For cooling only people during sports activities or in hot climates, gel-containing garments are known, see e.g. W01996019126 or US5755110. The garment has a plurality of pockets to contain polyacrylamide beads that absorb water to form a gel, The gel then can be cooled or frozen to give a cooling effect to the wearer of the necessarily wet, cold or frozen garment.

Clearly the use and usefulness of these solutions are limited to the external supply of water by the user, and the mechanical cooling is exogenous.

There are also simple yarns that exploit the inertization of epidermal fluids for a spontaneous control of perceived body temperature.

There are coatings that through the sole use of a highly inertial material (gel) delay the perception of heat or cold.

The object of the invention is to improve this state of the art, in particular by making the above-mentioned functions (A) and (B) coexist in a single product. This object is achieved by what is defined in the appended claims, wherein the dependent claims define advantageous variants.

An aspect of the invention relates to an element for regulating the temperature of a surface with which it is in contact, comprising

- a first outer layer of breathable textile, preferably hygroscopic, material overlaid on

- a second inner layer of breathable and preferably water-repellent textile material (to be applied e.g. on the skin). wherein the first layer has hydrophilic hygroscopicity greater than or equal to that of the second layer.

The temperature-regulating element may optionally comprise a third layer, placed between the first and second layer. In this case, the first layer has hydrophilic hygroscopicity greater than or equal to that of the second layer, but still less than that of the third layer.

A preferred field of application of said element, which has proven to be very effective, is thermoregulation of the human body. However, the aforementioned element can be applied to any body to be thermoregulated, and at any inclination, such as a panel in construction, panels for ventilated walls or roofs, seat spacers, mattresses, upholstery in general, both thermal and athermal blankets, work jackets and coats, T-shirts, shoes and headgear, and medical supports, complete garment fabrics, agro-textile, etc.

In such applications it is advantageous to use 3D (three-dimensional) fabrics as layers, i.e. fabrics that have a pronounced third dimension in the direction of thickness, whether they are woven, knitted, braided or stitched with possible nonwoven (TNT) inserts.

An advantageous embodiment is based on a fabric comprising three or more sets of yarns, e.g. differentiated according to the interfacial tensions, to obtain a 3D interlaced, non-interlaced or fully interlaced fabric (shuttle weaving) or 2.5 D (pile), according to Khokar's classification (1998), in order to obtain solid, semi-solid, hollow, shell or nodal structures that can also include 3D nonwoven. The realization may be done both on 3D knitting and 3D weaving machines, whether circular, straight or with seamless technology.

The characterization of hydrophilic hygroscopicity is given by the interfacial tension, i.e. (see Figs. 1 and 2) the force per unit length acting tangentially to the separation surface 10 between liquid 12 and another phase, opposing the increase in interface surface area. The closer the contact or separation angle a approaches 180°, the lower the hydrophilic hygroscopicity. The contact angle a is determined to measure the wettability of surfaces. Taken a drop of liquid 12 deposited on a solid surface 10, the contact angle a is defined as that angle formed by the liquid-gas interface with respect to the solid surface 10. By convention, surfaces having a contact angle a with water greater than 90 degrees are considered hydrophobic and surfaces with angles a less than 90 degrees are considered hydrophilic.

This feature can be inherent spontaneously in the nature of the yarn and add to the porosity resulting from the type of fiber that is generally higher for natural yarns (e g. wool, cotton, etc.), to follow generally artificial materials obtained from the processing of natural raw materials of organic origin (e.g. acetate, viscose, etc.), and finally synthetic materials (e.g. polyester or polypropylene, etc.), or decreased with water repellency treatments or, on the contrary, increased with an increase in the surface of the yarn (in the case of natural yarns e.g. by carding, and in synthetic materials e.g. by drawing with an indented surface),

The adsorption surface can also be further increased by mesh processing.

The first layer, the one that would be the outermost layer in a garment, with function of amplifying the body surface of greatest evaporating perspiration, preferably is a layer with strong adsorption properties, i.e. with angle a < 90 degrees. Maximum wettability occurs when the angle a is equal to or close to zero. The second layer is the one that, in a garment, would be the innermost layer (e.g. in contact with the skin). Preferably the second layer is a layer with low adsorption properties with angle a greater than or equal to that of the first layer. There can be equality because there is the boost given by evaporation (Venturi effect). Preferably, the element comprises interstitial alveoli between the first and second layers, e.g. cavities or cells either in the form of preferably - in use - horizontal channels, or closed pockets on four sides. The channels may extend parallel and/or orthogonally to the separation surface between the first and second layers. The alveoli may be e.g. cavities present in the body of the first and/or second layer. Preferably, the interstitial alveoli are solid, or semi-solid, or hollow, or shell or nodal structures formed between said two layers.

For example, the alveoli contain one or more hydroretentive substances or means, preferably retained and/or contained in yarns. The hydroretentive substance or means may also be in the form of granules or beads, provided that they are kept by small compartments and/or horizontal in order to prevent deposition by gravity, or in flakes so as to be spun or compressed into TNT ( nonwoven ).

Preferably, the alveoli are arranged in the element so that they are little in contact with - or stand at some distance from - the contact surface, to allow room for air to circulate in two directions through the element. Even more preferably, the alveoli are arranged in the element so as to be at the interface (or contact surface) between the first and second layer, in particular a half of the alveolus is formed within the first layer and a half of the alveolus is formed within the second layer.

It is advantageous for the same air to enter and leave the element. For this purpose it is possible to exploit the natural inhomogeneities in the local density of a fabric which develops in space as an ordered or random succession of full and empty spaces Air can sneak into the voids to cross the thickness of the element in one direction or - better - in two opposite directions (orthogonally to the major surface of said two layers).

The one or more hydroretentive substances or means has the characteristic of being a water retentor compensatory and dampening of the aforementioned functions (A) and (B). The second layer has the function of conveying sweat or water both towards the first layer and towards said substance or means, keeping the surface of least contact as dry as possible.

In order for the above mentioned components of the element to perform their functions in the best possible way, it is preferable that all three are in contact with each other. With the above features, the second layer does not get soaked with sweat or water but pushes it towards the first layer, which absorbs it and from which it can evaporate bringing a first cooling to the air between the cells and the surface of least contact (e.g. skin).

Through the control of the conveyance of water molecules in both liquid and gaseous aggregation coming mainly from the human body - or from a surface of least contact - it is possible to control the thermal behavior of the element in the phase of greater overheating: the two layers draw energy from the human body through an endothermic action in the state transition with the evaporation favored (also) by an air flow directed from the outside through the two layers and by an outwardly-directed air flow between the support surface (e.g. the skin) and the first layer.

A further action of thermal control occurs thanks to the inertialization provided by the high thermal capacity of the water contained in the retentive substance or means. The water retained by the retentive substance or means acts as a thermal flywheel and creates a protection due to its thermal inertia in case of sudden thermal variations. This is due to the high effusivity and low diffusivity of the water retained in the retentive substance or means. In addition, when the water retained by the retentive substance or means evaporates and passes through the first external layer, continuing to moisten it, the evaporation subtracts heat from the element as a whole and, on the other hand, from the underlying body, increasing the first moment of cooling that affected only the air between the interstices or cells, while now it also leads to the lowering of the substance's temperature.

Preferably the hydroretentive substance or means has angle a close to zero (e.g. 20 degrees), near zero (e.g 10 degrees) or zero.

Preferably the alveoli have bigger dimension than the volume of the hydroretentive substance or means contained therein. That is, between said substance or means and the inner surface of the respective alveolus there is preferably an empty space to allow the substance to expand while absorbing water. The advantage, besides increasing the absorbing surface, is to retain liquid inside the substance or means until it is expelled therefrom and made evaporated in an amount dependent on the thermal condition of the element resulting from the thermo-hygrometric inputs of both the underlying body and the external environment.

Said substance or means is capable of drawing water either in vapor form or in liquid form (e g from sweat)

Said substance or means may be e.g. any superabsorbent hydroretentive gel such as SAP, or PAM or PAN, whether synthetic or semi-synthetic, even in combination with each other. E.g. the gel is generally a polymer, such as polyacrylate or polyacrylic acid, polyacrylonitrile, acrylamide, etc.

Said substance or means also has the advantage that it adds absorption capacity - twenty to hundreds of times its own weight - to the normal physical function of adsorption given by the type of fiber, and prevents water from flowing by gravity.

Another advantage is that the element offers a cooling action on the body by using evaporation in a controlled manner.

Said substance or means is preferably retained and protected internally between the first and second layers. When the ionic dissociation determines a consequent osmotic pressure from said substance or means towards the outside, there is expulsion of water molecules and a more modest retention thereof in absorption in the first outer layer.

In said substance or means, water molecules, in both liquid and gaseous aggregation, move toward the central alveoli containing said substance or means, thanks to the water repellency of the second layer and the spontaneous outward thrust of the vapor.

Given the semi-fluid nature of the substance or means, in order to avoid leakage - if the absorption power exceeds the viscosity limit - it is preferable to support the substance or means with a hygrophilic fiber, better if very hygrophilic, both for interfacial tension and porosity. The fiber has adsorption functions in order to avoid the dispersion of the semi fluid. Preferably then the hydroretentive substance or means has a low concentration of crosslinker to allow gel blocking but not the "fisheye" (see Buchholz and Graham, 1998).

An advantage given by the combination of the above components is that the cooling action increases or decreases spontaneously in proportion to the body sweat or water vapor emitted by the person for having exceeded the ideal body temperature as a result of either the consumption of calories via movement or external supply from the environment. Therefore, the combination of components automatically regulates heat removal through endothermia to maintain the underlying body at an almost constant temperature in non stress situations given the high effusivity and low inertial diffusivity of the substance or means.

The first and second layers may be any panniculus, woven or textured fabric, integument, membrane, consisting of filaments or burrs of various materials whether natural, synthetic or artificial

The first and second layers preferably are generally a fabric, e.g. a drapery, a woven or textured fabric, a tegument, a membrane, consisting of filaments or burrs of different materials, differentiated, e.g. both by characteristics of the component (yarn, felt, nonwoven fabric, etc. ) and by nature (natural, synthetic, artificial) Said substance or means is e.g. any super-absorbent hydroretentive gel such as SAP, or PAM or PAN, whether synthetic or semi-synthetic, even in combination thereof. E.g., the gel is generally a polymer, such as polyacrylate or polyacrylic acid, polyacrylonitrile, acrylamide, etc. The hydroretentive substance or means may also be in the form of granules or beads.

In particular, the aforementioned element forms overall a composite fabric. In a variant, said substance or means is not in total contact with the surface to be thermoregulated. In this case, direct air passages are present to facilitate the upward thrust of water in both liquid and vapor form.

Another aspect of the invention relates to a garment made from - or comprising - said composite element or fabric. The garment is e.g. a T-shirt, pants, a face mask, a cap, a protective blanket, etc.

Note in general that

• the temperature control element may be configured so that the water-repellent element captures water also from external (re)condensation, to allow both liquids and steam to reach the two yarns/fabrics that will expel them;

• an advantage of said substance or means, especially in the form of an inerting gel, is that it is capable of quickly absorbing and retaining water, preventing it from running off. Such water, which may be sweat, rain, or liquids in general, allows it to be saved and then expelled by evaporation in a progressive manner and proportionally to the external temperature;

• the element is configured to pass air through both the first and second layers;

• the element allows to recover and "recycle" what has been emitted;

• for cooling one doesn't need to put the material in the freezer and then put it on with considerable shivering, but the cooling is progressive, spontaneous and more durable.

The materials of the temperature regulating element do not have a flat surface and stay raised to let air pass which really dries the skin. The aforementioned materials could also have a flat bottom but being perforated in their entirety they still obtain the effect of "exchange radiator" allowing the passage of air and the withdrawal of heat as well as allowing the evaporation of water contained/kept in the intermediate layer.

The following description relates to a preferred embodiment of a cooling element or layer and will highlight further advantages thereof, referring to the accompanying drawings wherein:

- Fig. 1 shows a representation of a surface with high hydrophilic hygroscopicity; - Fig. 2 shows a representation of a surface with low hydrophilic hygroscopicity;

- Fig. 3 shows a schematic partial cross-section of a fabric;

- Fig. 4 shows various types of weaves and fronts applicable to a fabric according to the invention. In the figures equal numbers indicate equal or similar parts, and the element is described as in use. To avoid crowding the drawings not all equal elements are marked.

A fabric 40 (fig. 3) comprises a first outer layer 20 overlaid on a second inner layer 30. The inner layer 30 in use contacts - or is closest to - a support surface S, e.g. the skin S of the user, to the extent/in the form of least contact. The outer layer 20 in use contacts - or is closest to - the environment. The support surface S may be curved or flat.

The layer 20 has hydrophilic hygroscopicity greater than, or equal to (being able to benefit from vapor thrust by venturi effect), that of the second layer 30. According to the characterization in Figs. 1 and 2, a water droplet in the layer 20 has contact angle a less than or equal to the contact angle a in the layer 30. E.g. the layer 20 has contact angle a less than or equal to 90 degrees.

E.g. the layer 30 has contact angle a greater than or equal to 90 degrees.

To improve thermal regulation, preferably the fabric 40 comprises alveoli 34 located between the first and second layer 20, 30. The alveoli 34 contain one or more hydroretentive substances or means 32, e.g. a gel, preferably retained and/or contained in yarns or fibers.

The retentive substance 32 is able to retain water, therefore due to the high thermal capacity of water the retentive substance acts as a thermal flywheel. In addition, if the heat emitted or received by, for example, the human body is sufficient for the well-being of the same because contained in the comfort values, the water retained by the substance 32 evaporates, and the evaporation subtracts further heat from the fabric. Such values preferably coincide with the values of the temperature that allows the substance 32 to evaporate, and in particular to subtract up to 2210 J/gr.

Preferably, the hollow, shell or nodal alveoli 34 are larger in size than the volume of the water-retaining substance 32 contained therein. Preferably there is a gap between the substance 32 and the inner surface of the respective alveolus 34 to allow for expansion of the substance 32 as it absorbs water.

The substance 32 is capable of drawing water both in the form of vapor from the moisture internal to the fabrics, and in liquid form as sweat The substance 32 may be e.g. any hydroretentive gel, such as SAP or PAM or PAN, whether synthetic or semi-synthetic, even in combination with each other. E.g. the gel is a polymer, such as polyacrylate or polyacrylic acid, polyacrylonitrile, acrylamide, etc.

E.g. the substance or means 32 has a contact angle a of less than 90 degrees With the above characteristics the two layers 20, 30 and the substance 32 work synergistically. When the human body sweats or emits water vapor, the layer 30 does not soak up water, with the frequent discomfort that the garment drips with sweat but the person is still warm. Instead, the layer 30 pushes water and water vapor towards the layer 20 and the substance 32, which absorb it and from which it can evaporate, bringing coolness first to the air contained in the spaces between the alveoli 34, and then to the substance 32, and finally to the skin, i.e. the contact surface S.

The arrow F indicates a flow of air penetrating the fabric 40 from the outside to the inside. For example, the air arrives in - and/or is favored by - empty cavities 50 formed by the natural texture or irregularity of the layer 30. The airflow may also flow back outward from the inside.

The substance 32 may be flanked by a hydrophilic substance or fiber 36. The fiber or substance 36 has an adsorption function to prevent dispersion of the semi-fluid.

The fabric 40 may make up e.g. a T-shirt, pants, a face mask, a cap, or a thermal blanket. Fig. 4 illustrates some textures for a fabric according to the invention. Yarn structures with cells of - or containing - the substance 32 inside can be seen (see also arrows).