Field of the invention

The present invention refers to a hot melt adhesive composition, more specifically, to a hot melt adhesive composition for disposable medical articles, specifically, to an X-rays detectable hot melt adhesive composition that allows the identification of non-woven material left inside the patient body during surgical procedures, therefore, avoiding additional surgery to remove it.

Summary of the invention

The present invention refers to a hot melt adhesive composition. Hot melt adhesives are applied in a molten state, thus, at high temperatures, over a material surface and harden during the cooling process in which they bond, at least, two materials together. These adhesives are supplied in the solid state and are then melted and applied while fluid. Depending on its properties, the application temperatures can range from 100 °C to 200 °C.

Hot melt adhesives are advantageous due to their solvent free formulation, fast setting since it occurs during the cooling process, can be repeatedly melted, and applied, extruded in several formats, and applied by different systems. These benefits combined with increased concern with energetic and environmental resources leverage the use of hot melt adhesives by several industrial sectors on a global scale. Besides their ability to correspond complex industrial requirements, hot melt adhesives can be formulated to possess high performance with a low cost. Due to their security and non-toxicity, hot melt adhesives are suitable for, but not exclusively, hygiene and the medical industry.

A typical hot melt adhesive composition includes a polymeric component, a resin component, and a plasticizer component. Moreover, it can include wax, antioxidant, and mineral fillers, depending on the desired properties. Apart from the technical requirements, the component selection is dependent on the substrate that will be applied on. It is fundamental for the hot melt adhesives used in the medical industry to possess a high adhesion capacity with the different materials that are used in this sector, also referred to as substrates. Depending on the substrate, the chemical base of the hot melt adhesives that are used in the medical industry can be divided into polyolefins, thermoplastic elastomers, acrylates, and polyurethanes. Due to the advanced production processes of the medical industry, including automatic processes and several nozzles, it is fundamental for the hot melt adhesive to be versatile in the operational window and to be able to adapt to the fast production speed. Last, the hot melt adhesive must resist the sterilization process to which the final product is submitted to.

Concerning the medical industry, specifically surgical interventions, the surgical environment is largely composed of non-woven disposable articles, such as the protective garment, sponges, gauzes, and compresses. Furthermore, in a surgical environment, the surrounding area of the incision is in contact with non-woven material and these products must assure hygienic and sanitary security.

On a surgical procedure, the blood flow from the patient is inevitable and the incision area is often considered an area of high blood flow. During surgical procedures, disposable nonwoven materials are used to absorb the blood and clean the bleeding area. Unfortunately, in situations of high blood flow the soaked non-woven disposable articles can be imperceptible to the naked eye and mistaken with the blood of the patient. Generally, the surgical material that is used during a procedure is controlled to identify situations in where these are forgotten on the body of the patient. Sometimes, even when this control does not identify any missing material, the patient might present considerable discomfort and the possibility of forgotten surgical material inside its body needs to be discarded. For most of the cases, this can only be done by submitting the patient to another surgical procedure, that may or not be justifiable, and additional possible complications and discomfort.

Considering this, it is necessary to avoid that surgical material, in particular, non-woven disposable articles, is forgotten on the patient body, increasing the associated risks and further surgical processes. Thus, some alternatives are being developed to easily identify nonwoven disposable articles before closing the incision, such as X-rays detectable non-woven articles. An example of this are the surgical complexes that are composed of X-rays detectable materials and gauzes that are sewed with X-rays detectable fibres.

Given this information, there is the obvious need to develop an alternative solution that, not only addresses the mentioned problems and risks associated with surgical procedures, but also simplifies the production process of X-rays detectable disposable non-woven articles suitable to be used on surgical procedures.

The present invention relates to a hot melt adhesive for the medical industry, specifically for disposable non-woven articles used in surgical procedures, that has in its composition minerals that are X-rays detectable, thus, making the hot melt adhesive composition X-rays detectable. This hot melt adhesive composition is incorporated on the disposable non-woven medical articles that might be in direct contact with the patient body. The hot melt ad hesive composition must present a good processability, so it is easily used on the production process of the disposable non-woven medical articles, and should not affect their absorption capacity, flexibility, and resistance to the sterilization process.

Background of the invention

Since the first reports medical malpractice due to forgotten disposable articles on the patient bodies after a surgical procedure that inventions to avoid these situations are being published. The scope of these inventions is mainly to provide a solution that allows the visual identification of the disposable non-woven articles by making them X-rays detectable, avoiding further complications for the patient.

Document CA2487674A1 describes an invention for the surgical field that comprehends a sewed woven sheet with X-rays detectable material (60% barite).

Document CN101244287A refers to a disposable non-woven article for medical bandages, such as gauze and degreaser non-woven, containing an X-rays detectable material, composed from 40% to 70% barite. This X-rays detectable material is applied directly on the surface of the non-woven disposable articles.

Document W02011/014907A1 refers to a surgical article with different non-woven layers with an X-rays detectable material that is hydraulically entangled in the non-woven material.

Document WO2015/035282A1 refers to a polyurethane thermoplastic component combined with barite nanoparticles for the healthcare industry, namely hygiene disposable articles, such as catheters or others containing polyurethanes in its composition and associated with diagnostic means or therapeutic procedures, allowing the radiopacity of these articles. Document US2004127614A1 describes a polyolefin composition for several uses, namely hot melt adhesives. Although the polymeric chemical base that is used is the same as the present invention, compositions with antioxidants, resins or contrasting components are not referred in this document, being only mentioned as optional components. Additionally, there is no mention of using this invention for detectable X-rays articles, being the barium sulphate used as a filler and not for its X-rays detectable properties.

Document CN112266756A describes a hot melt adhesive that comprises an X-rays detectable material to allow the radiographic inspection in industrial assembly lines, in order to improve the quality control in which this adhesive is used.

Document CN 103517692A refers an X-rays detectable adhesive bandage and a method of manufacturing an X-rays detectable adhesive bandage, wherein said X-rays detectable adhesive bandage has a high sensitivity to detection by an X-rays detection device as well as a high sensitivity to detection by a metal detector.

Advantages of the invention

By analysing the state of the art, it is possible to conclude that barite/barium sulphate is widely used for being X-rays detectable. However, it is not common to use it in disposable non-woven articles since it alters their performance and the process to incorporate it on the disposable non-woven articles is time consuming.

The present invention relates to a hot melt adhesive for the medical industry, specifically disposable non-woven articles to be used in surgical procedures. The hot melt adhesive composition comprises X-rays detectable minerals that are compatible and stable with the remaining components. This hot melt adhesive composition is suitable for any disposable nonwoven article that might be or not be in direct contact with the interior of the patient body. Thus, the hot melt adhesive is biocompatible, anti-irritating and no allergic. It is fundamental that the hot melt adhesive composition behaves as an inert when in contact with the patient body, to assure its comfort, and to comply with the legal requirements of the medical industry.

This hot melt adhesive must possess a high adhesion to the substrates and during the medical procedure must not detach from the substrates, must resist direct contact with body fluids and the handling pressure. Thus, the hot melt adhesive composition should not have residual tackiness nor leave residues on the surfaces that it contacts. Additionally, the present invention should guarantee that the properties of the disposable non-woven articles, such as absorption capacity, flexibility, and resistance to the sterilization process, are not affected. On top of this, the hot melt adhesive should have a short open and setting time in order to be easily applied on fast industrial lines. Thus, the implementation of the present invention makes the disposable non-woven articles for medical procedures to be detectable by X-rays and, also, to maintain its original characteristics. The hot melt adhesive composition of the present invention is applied on the disposable non-woven articles and develops a strong adhesive bond that assures the quality of the final product and the patient security.

Detailed description of invention

The object of the present invention is a hot melt adhesive that is detectable by X-rays and is intended for application, namely, but not exclusively, in the medical industry, more specifically, in non-woven materials used in a surgical environment.

Another object of the present invention is a hot melt adhesive that incorporates in its composition minerals that are detectable by X-rays in an effective and stable way for long periods of time, when subjected to high temperatures.

Yet another object of the present invention is an X-rays detectable hot melt adhesive, in which properties such as viscosity, softening point, open time and setting time can be controlled by varying the composition of each element of the composition.

By "contrast agent" is meant one or a mixture of minerals that are radiopaque in X-rays.

By "substrate" is meant the material or surface of the material to which the hot melt adhesive is applied and/or directly contacts. In the context of disposable articles in the medical industry, the most common substrates are polyethylene film and polypropylene non-woven fabric.

By "open time" is meant the maximum time period, after the hot melt adhesive is applied to the first substrate, in which it is possible to effectively bond a second substrate.

By "setting time" is meant the minimum time interval in which pressure is required for two substrates to bond effectively. Thus, the setting time is associated with the speed with which the adhesive recovers its cohesive forces. By "base polymer" is meant the polymeric materials that contribute to the fundamental characteristics of the composition and form the foundation of the composition. Thus, the remaining components of the composition have the function of altering or improving properties of the polymeric base.

By "compatibility and stability with the rest of the composition" is meant the ability to form a homogeneous mixture, without phase separation, even after exposure to high temperatures for extended and repetitive periods of time.

According to the invention, the hot melt adhesive comprises:

- a polymeric component comprising of at least one polyolefin polymer, which due to its rheological properties is capable of forming a homogeneous mixture with the remaining components of an adhesive, controlling characteristics such as viscosity;

- a resin component comprising of at least one resin of synthetic origin;

- a contrast agent, comprising of a mixture of minerals with defined particle size and compatible with the rest of the composition;

- an antioxidant component comprising at least one phenolic antioxidant; and optionally:

- a plasticizer component comprising at least one plasticizer capable of forming a homogeneous mixture with the contrast agent and the polymeric component, in cases where the polymeric component alone is not capable of doing so.

Polymeric Component

The key component of the hot melt adhesive composition is the polymeric component, being responsible for the rheological behaviour of the final product.

Suitable polymers for the adhesive of the present invention are selected, namely, but not exclusively, from: olefin block copolymers, isostatic propylene and ethylene copolymers, coupled amorphous polyolefins of butene and/or propylene, ethylene and octene copolymers, metallocene-catalyzed polypropylene or polyethylene homopolymer.

The polymeric component content should be up to 80% by weight of the hot melt adhesive, preferably between 10% and 70%, more preferably between 30% and 65%, even more precisely between 40% and 60%, more concretely between 50% and 55%. Resin Component

The main purpose of the resin component is to ensure effective adhesion to the materials used. As the hot melt adhesive of the present invention is intended to be anti-irritant and anti-allergic, it must consist of a hydrocarbon resin, selected, in particular, but not exclusively, from among : C5 aliphatic, C9 aromatic, C5 aliphatic - C9 aromatic and dicyclopentadiene (DCPD), more preferably C5 and C9 resins and even more preferably hydrogenated C9 aromatic resins.

The hydrocarbon resin content should be up to 40% by weight of the hot melt adhesive, preferably between 1% and 30%, more preferably between 2% and 20%, even more preferably between 3% and 15%, more concretely between 6% and 10%.

Plasticizer component

The use of the plasticizer component simultaneously allows the melting of the polymer and the adjustment of the viscosity and softening point of the hot melt adhesives to values considered adequate, so that it can be easily applied in industrial lines of disposable articles.

Tests were carried out comparing the hot melt adhesive of the present invention with other adhesives present in the state of the art. In order for the other glues present in the state of the art to be able to present appropriate qualities for use in disposable medical articles, it was necessary to add a plasticizer component. The hot melt adhesive of this invention presents a plasticizer component as an option, not being essential for its composition, and comprising at least one liquid plasticizer at room temperature, selected, in particular, but not exclusively, from saturated hydrocarbons, polybutenes, mineral oils, hydrotreated naphthenic or paraffinic oils, preferably highly hydrotreated naphthenic oils.

Contrast agent

The contrast agent comprises a barium sulfate compound precipitated with, namely, but not exclusively, 98,5% barium sulfate. Barium sulfate is an inert mineral, insoluble in water, acid base and organic solvents, free of impurities, and with a particle size between, but not exclusively, 0,001 and 6 pm in mean diameter. The contrast agent content should be up to 65% by weight of the hot melt adhesive, preferably between 10% and 60%, more preferably between 25% and 55%, even more precisely between 30% and 50%, more specifically between 35% and 45%, more concretely between 38% and 42%.

Antioxidant component

The use of the antioxidant component aims to prevent the degradation of the hot melt adhesive by the action of heat, either during its production, during application or during storage of the final product. For the present invention, the use of an antioxidant component comprising at least one primary, secondary or multifunctional antioxidants is particularly useful. Thus, selected antioxidants are considered suitable, namely, but not exclusively, from: phenolic antioxidants, phosphites, thioesters, dioctadecyl ester of thiodipropionic acid or a mixture of these, the combination of phenolic antioxidants and dioctadecyl ester of thiodipropionic acid being particularly suitable.

The content of the antioxidant component suitable for the present invention corresponds to up to 15% by weight of the hot melt adhesive, preferably between 0,1% and 10% and more precisely between 0,2% and 2%, even more concretely between 0,2 % and 0,9%.

Process for production of the hot melt with the incorporation of contrast agents

The process for producing the hot melt adhesive detectable in X-rays, which is intended for application, in particular, but not exclusively, in the medical industry, more specifically, in non-woven materials used in a surgical environment and which includes in its composition a contrast agent, comprises mixing, with constant agitation, the resin component and the antioxidant component at a temperature between 100 °C and 200 °C, more precisely between 120 °C and 180 °C, more specifically between 150 °C and 170 °C, until a paste with a homogeneous appearance is formed. To this paste, the contrast agent is gradually added. Finally, the polymeric component is mixed with this paste, with constant agitation, until it melts completely, and the paste presents a homogeneous, opaque, and fluid appearance.

Embodiments of the invention To verify the results obtained by the composition, as well as its comparison with state-of-the- art compositions, several tests were performed, the results of which are shown in Table 1.

One of the tests carried out is the thermal stability test, which verifies whether phase separation occurs, which, if so, indicates the incompatibility of the formulation.

The embodiment of Example 1 is presented regarding the composition of a hot melt adhesive for the construction of disposable non-woven articles in the medical industry, with technical properties, namely viscosity and softening point considered appropriate. However, this composition does not include minerals, so it is not considered suitable for the present invention and is presented for comparison purposes only.

The embodiment of Example 2 is presented regarding the composition of a hot melt adhesive for the construction of disposable non-woven articles in the medical industry with technical properties, namely viscosity and softening point considered appropriate. This embodiment contains a mineral component in its composition. However, this composition contains a polymeric component different from that described in the invention, more specifically, a copolymer of ethylene and butyl acrylate, and a plasticizer component, so it is not considered suitable for the present invention and is presented only for the purposes of comparison. This composition, due to the different polymeric component and to the presence of a plasticizer component, does not present adequate thermal stability, verifying phase separation after exposure to 180 °C for an extended period.

The embodiment of Example 3 refers to the optimization of the properties referred in Example 2, which was obtained by replacing the polymeric component of ethylene vinyl acetate copolymer by a polymeric component of polyolefin and, furthermore, removing the plasticizer component. All desirable technical characteristics were maintained: excellent adhesive capacity, flexibility, resistance to sterilization processes, softening point and viscosity that allow easy application in the final product.

#1 - Test Method : Brookfield, Thermosel System, ASTM D3236

#2 - Test method : Ring and Ball, ASTM E28

#3 - Test method : Thermal stability analysis according to ISO 10363, at 180 °C