Field of Invention

The present invention relates to a method of surface modification of ceramic objects and more particularly, relates to repair of worn out surface of ceramic hand mold by surface re- coating process.

Background of the Invention

Protective gloves are generally worn by individuals in order to protect their hands from various chemicals, materials, and objects which may irritate, damage, dry out, or otherwise negatively affect the user's skin, and which may be harmful or potentially harmful if allowed to contact or permeate the dermal barrier. Scientists, healthcare professionals, chemical industry workers, cleaning service workers, food processing workers, food handlers, law enforcement workers, beauticians or other workers having special protection needs, wear such gloves in their occupational environment.

Typical manufacturing process of disposable protective gloves begins with washing of glove formers or hand molds using water, acid and alkali, followed by dipping into coagulant mixture and dipping into a tank containing latex or synthetic rubber material. Further the process involves chilling, dripping, gelling or curing, leaching and stripped off from the formers for testing prior to packaging.

In glove manufacturing process, the ceramic hand mold, also known as former is commonly used to manufacture gloves through dipping process. However, continuous dipping process leads to surface damage of former, also referred to as worn out former. The worn out degree of a former is always random and not traceable, as damage to the surface is mainly caused during the dipping process mainly attributed to both chemical and mechanical effects, thus causing uneven thickness ultimately resulting in production of defective gloves.

Glove former surface modification methods discussed in the prior art fails to address the issue of worn out formers, without appropriate repair methods these worn out formers or hand molds are classified as disposable material, therefore leading to low shelf life and increased wastage of formers in glove manufacturing industry. In addition, conventional methods for former surface modification also fails to teach customization of surface texture on finished goods of glove formers or ceramic hand molds. Moreover, glove formers discussed in the prior art are generally subjected to surface modification process prior to last stage of former firing. The surface modification process comprises sand blasting, which is generally carried out on ceramic green body possessing lower material hardness, for example: 0.4 to 1.2 GPa, since lower material hardness allows easier control of the sand blasting process.

Therefore, there exists a need for methods of repair or recycling of worn out ceramic hand molds or glove formers in order to increase the former shelf life and customized surface modification allowing versatility in creating new ceramic hand mold surface texture or former surface texture.

Summary of the Invention

The present invention relates to a method of surface modification of a ceramic hand mold used in glove manufacturing, the method comprising following steps: i) providing a ceramic hand mold for repair; ii) surface re-coating of the ceramic hand mold using a matt or glossy glaze solution comprising 30 to 70 percent total solid content (TSC); iii) thermal processing through kiln firing temperature between 1120 and 1380° C; and iv) sand blasting on finished ceramic hand mold.

In another embodiment, the ceramic hand mold of the present invention comprises of worn out or surface damaged ceramic hand mold. The method of the invention provides repair of surface damaged or worn out ceramic hand mold using surface re-coating process.

Brief Description of the Drawings

Other objects, features, and advantages of the invention will be apparent from the following description when read with reference to the accompanying drawings. In the drawings, wherein like reference numerals denote corresponding parts throughout the several views: Figure 1 is a flow diagram of a method of surface modification of a ceramic hand mold according to an embodiment of the present invention.

Figure 2 is a perspective view of a ceramic hand mold with finger texture surface modified using sand blasting process according to an embodiment of the present invention.

Figure 3 is a perspective view of a ceramic hand mold with modified surface texture in the crotch area according to an embodiment of the present invention. Detailed Description of the Preferred Embodiments

As used herein, the terms ceramic hand mold or glove former or former refer to a hand shaped ceramic mold used for manufacturing gloves made of natural or synthetic rubber material. Further, it should be understood that the embodiments described herein, could be used to repair or restore the worm out surface of any ceramic object. The ceramic hand mold is presented as representative example of a ceramic object that could be repaired using the process described herein.

The present invention will now be described in detail with reference to the accompanying drawings.

Referring to Figure 1 , the present invention discloses a method ( 100) for surface modification of a ceramic hand mold used in glove manufacturing, the method comprising steps: i) providing a ceramic hand mold for repair (1 10); ii) surface re-coating of the ceramic hand mold using a matt or glossy glaze solution comprising 30 to 70 percent total solid content (120); iii) thermal processing through kiln firing at temperature between 1 120 to 1380° C ( 130); and iv) sand blasting on finished ceramic hand mold ( 140).

In an embodiment of the present invention, the ceramic hand mold comprises worn out ceramic hand mold or surface damaged ceramic hand mold. The method of surface modification comprises repair of worn out or surface damaged ceramic hand mold leading to minimized wastage of formers or hand molds and also increased shelf life of glove formers thereby benefiting the glove manufacturing industry. Oxides commonly employed to create matt glazes are A1203, Si02, K20, Na20, CaO, MgO, Zr02 and for glossy glazes are B203, A1203, Si02, K20, Na20, Li20, CaO, MgO, ZnO, Zr02. The required amount of any oxide depends on the identity and quantity of other oxides present, the firing temperature, and many other variables such as what ceramic it is applied to. According to an embodiment, firing temperature is within a range of 1120 - 1380° C. Glaze defects might occur during re-coating process mainly due to overfiring or underfiring. Other common causes of glaze defects are difference in coefficient of thermal expansion between body and the glaze, defective application, adhesion defects which also leads to formation of hair cracks, chipping and peeling.

Thermal processing by kiln firing forms an essential part of the manufacture and surface modification of ceramic hand molds, which require heat treatment, often at high temperatures. During this process, chemical and physical reactions occur that permanently alter the unfired ceramic body. The final characteristics are determined by the composition and preparation of the ceramic body, by the temperature at which it is fired, and by the glazes that may be used. The surface modification method of the present invention can be used for manufacturing glazed ceramic hand mold as well as unglazed ceramic hand mold or glove former using sand blasting on finished goods of ceramic hand molds rather than ceramic green bodies. Sand blasting on finished ceramic hand molds offers versatility in creating new ceramic hand mold surface textures suitable for both latex glove production and nitrile glove production.

In addition, the finished goods of ceramic hand molds exhibits higher surface hardness, for example the ceramic material hardness of finished goods falls in the range of 12.3 to 22.0 GPa comparing to the ceramic green body with lower material hardness of about 0.4 to 1.2 GPa.

Sand blasting process offers formation of customized surface roughness on the finished goods of ceramic hand molds such as variation in surface roughness at the crotch, cuff and finger tip surfaces of formers as desired. For example, increased roughness at the crotch area results in higher latex pick up thus forming gloves with thicker crotch area. Similarly, textured finger tip of ceramic hand molds results in gloves with thicker finger tips which otherwise are normally prone to laceration while usage.

In an embodiment, the sand blasting process comprises the following steps: i) preparing sand blasting equipment and sand blasting media; ii) feeding sand blasting media into and transmitting sand blasting media to an air vent outlet by compressed air, such that the sand blasting media impacts the surface of ceramic formers at high speed; and iii) selecting appropriate blasting interval for achieving desired feature of former with controlled surface roughness.

In an embodiment, the present invention provides a method for recycling of worn out or damaged ceramic hand molds, thus increasing the shelf life of ceramic hand molds, which would be disposed otherwise as wastage due to wearing out. Thus, increased shelf life and recyclability achieved using surface modification process benefits glove manufacturing industry to a greater extent.

Examples

Example 1 : This example provides a solution to convert a glove former (200) with glazed fingertip into mild-glazed fingertip (210a, 210b, 210c, 210d and 210e) textured surface using sand blasting process on finished ceramic hand molds or formers as shown in Figure 2 of the drawings. Example 2: This example shows improvement of the crotch surface area (310a, 310b, 310c and 310d) using sand blasting process on finished ceramic hand molds (300) as shown in Figure 3. The roughness of the crotch area (310a, 310b, 310c and 310d) improves latex pick up which will result in improved glove quality. Example 3: In this example, operational specifications of sand blasting/abrasive blasting process, used on finished ceramic formers are given in the following table according to an embodiment of the invention. Sand blasting/ Abrasive blasting Process

Operating temperature(C) 30

Operating pressure (MPa) 0.2 - 0.5

Operating interval (Sec) 40- 600

Sand blasting media Alumina oxide and glass bead

Sand blasting media size (μπι) 20 - 320

Distance between sand blasting gun and ceramic 20 - 30

(cm)

As will be readily apparent to those skilled in the art, the present invention may easily be produced using additional methods without departing from its essential characteristics. The present embodiments is, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and all changes which come within therefore intended to be embraced therein.