ROLL TRANSFER COATING METHOD FOR THICK COATING SURFACE

Abstract

A roll transfer coating method for coating a coating material, which has been supplied from a coater head to a pattern surface of an intaglio roll, to a coating substrate. When the supply of the coating material is made, the supply is blocked off by a contact of the intaglio roll with the bottom surface of the coater head at a position facing the pattern surface of the intaglio roll, so that the coating material in a liquid state is supplied only into a recessed portion of the intaglio roll. Upon transferring the coating material onto the coating substrate which is being transported by a high-speed coating line, the temperature of the coating material on the pattern surface of the intaglio roll is maintained at or below a first form-changing temperature, so that the coating material in a gelled state is coated to the coating substrate.

Claims

1. A method for roll transfer coating of a thick coating surface, in which a coating material that has been supplied from a coater head to a pattern surface of an intaglio roll at a supply position is coated to a coating substrate at a transfer position after a rotation of the intaglio roll, wherein in a supply of the coating material from the coater head, the supply is blocked off by a contact of the intaglio roll with a bottom surface of the coater head at a position facing the pattern surface, so that a plastic molten resin coating agent in a liquid state is supplied only into a recessed portion of the intaglio roll, thus obtaining a thick coating surface on the coating substrate.

2. A method for roll transfer coating of a thick coating surface, in which a coating material that has been supplied from a coater head to a pattern surface of an intaglio roll at a supply position is coated to a coating substrate at a transfer position after a rotation of the intaglio roll, wherein in a supply of the coating material from the coater head, the supply is blocked off by a contact of the intaglio roll with a bottom surface of the coater head at a position facing the pattern surface, and a plastic molten resin coating agent in a liquid state is supplied only into a recessed portion of the intaglio roll, in a transfer of the coating material in the recessed portion of the pattern surface of the intaglio roll onto the coating substrate which is being transported by a high-speed coating line, a temperature of the coating material on the pattern surface of the intaglio roll is maintained, at the transfer position, at or below a first form-changing temperature, so that the coating material in a gelled state is, coated to the coating substrate, thus obtaining a thick coating surface on the coating substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 A front view of main components of a roll transfer device for implementing the invention of the present application.

[0019] FIG. 2 A developed top view of the pattern surface of an intaglio roll.

[0020] FIG. 3 A pattern developed view showing an embodiment of a coating pattern on the pattern surface.

[0021] FIG. 4 A vertical cross sectional view of a coating head (slot coater) taken at a slot groove position, illustrating a relation between the bottom surface of the coating head and the pattern surface when the supply of a coating material is blocked off.

[0022] FIG. 5 A vertical cross sectional view of the same as in FIG. 4, illustrating a state in which the coating material is supplied into a recessed portion of the intaglio roll.

[0023] FIG. 6 Shows the viscosity curve of a molten resin coating material, illustrating the relation between a change in temperature and a change in morphology of the molten resin coating material.

[0024] FIG. 7 A front view similar to FIG. 1, showing the temperature at each part of the roll transfer device and the change in the morphology of the molten resin coating material.

[0025] FIG. 8 Cross sectional views of the coating substrate after the molten resin coating material has passed a transfer position, where Figure (a) shows when the coating substrate is not permeable (such as a PP sheet), and Figure (b) shows when the coating substrate is permeable (such as a nonwoven fabric).

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] A roll transfer device for implementing the invention of the present application will be described with reference to FIG. 1. This device is constituted by a coating head (slot coater) 3, an intaglio roll 1, and a rolling mill roll 2. A coating substrate M (paper, nonwoven fabric, plastic sheet ((synthetic resin sheet)), etc.) is supplied to a transfer position between the intaglio roll 1 and the rolling mill roll 2.

[0027] The coating material supply position is set to be one-quarter rotation ahead of the transfer position, and the coating head (slot coater) 3 is installed in the coating material supply position.

[0028] In this coating head (slot coater) 3, the slot groove 4 is configured such that the center axis X in the longitudinal direction is horizontal in the radial direction through which the axis of the intaglio roll 1 passes, and the axis Y in the transverse direction is parallel to the axis of the intaglio roll 1.

[0029] The bottom surface 3a of the coating head (slot coater) 3 is provided so as to face and in contact with a pattern surface 1a of the intaglio roll 1. There is substantially zero gap is provided between the bottom surface 3a of the coating head (slot coater) 3 and the pattern surface 1a of the intaglio roll 1.

[0030] A coating pattern P is formed by forming recessed portions A on the pattern surface 1a of the intaglio roll 1.

[0031] FIG. 3 shows the coating patterns P1, P2, P3, P4, and P5 as examples of the coating pattern P.

[0032] The coating pattern P can be various kinds of displays, such as alphanumeric characters, Japanese characters, symbols, pictures, etc., in addition to the patterns and figures described above.

[0033] Because of the structure above, the pattern surface 1a of the intaglio roll 1 comes into, at its smooth surface B, contact with the bottom surface 3a of the coating head (slot coater) 3, except at the recessed portions A.

[0034] In the invention of the present application shown in the roll transfer coating device of FIG. 1, the reference numeral 5 is a valve mechanism, 6 is a supply pressure adjusting device, and 7 is a supply source of a plastic heat-molting resin or other such coating material (hot melt adhesives) HM. An electric heater 9 is installed in each device, and the heater of each device is controlled to maintain the temperature of each device at its set temperature.

[0035] Next, the coating operation according to the present invention will be described.

[0036] The coating material HM, which is made by heating and melting a plastic heat-melting resin or other such coating material into a liquid state, is supplied to the slot groove 3 of the coater head, and the coating material is supplied in a direction perpendicular to the pattern surface of the pattern roll.

[0037] Referring to FIG. 4, the coating material is discharged from a slot groove opening 3a of the coater head; however, the discharge onto the smooth surface B of the pattern roll surface 1a is prevented

[0038] Referring to FIG. 5, the slot groove opening 3a of the coater head faces the recessed portions A of the pattern roll surface 1a.

[0039] Thus, the slot groove opening 3a of the coater head is in an open state, and the coating material (hot melt adhesive) HM fills in the recessed portions A on the pattern roll surface.

[0040] Since the coating of the coating material onto the smooth surface B is prevented, only the recessed portion A is filled with the coating material HM.

[0041] A coating pattern P is formed on the pattern surface of the pattern roll and the pattern roll is moved by rotation to the transfer position.

[0042] At the transfer position, the coating material HM is transferred to form a thick coating surface HM onto the coating substrate M in the form of coating pattern P.

[0043] The rotation speed of the intaglio roll 1 is set to be synchronous with the transport speed of the coating substrate M.

[0044] Next, the change of state of the coating material such as a molten resin or other such material undergoes in the method of the present invention for the roll transfer coating of a thick coating surface will be described.

[0045] FIG. 6 shows the change of the state due to the heating temperature, wherein the temperature HM-T of the hot melt adhesive (coating material such as a molten resin or other such material) is shown in the X axis direction, and the substance form liquid-gel-solid HM-MS of the hot melt adhesive (coating material such as a molten resin or other such material) is shown in the Y axis direction.

[0046] Q is a viscosity curve indicative of the relationship between the temperature HM-T of the hot melt adhesive (coating material such as molten resin or other such material) and the substance form liquid-gel-solid HM-MS of the hot melt adhesive (coating material such as a molten resin or other such material).

[0047] Ta is a first form-changing temperature gelling point, and it corresponds to the change point from a liquid state to a gel state, that is, it corresponds to the temperature at which the change of state from a liquid state to a gel state begins.

[0048] Tb is a second form-changing temperature solidification point, and it corresponds to the temperature at which the change of state from a gel state to a solid state begins.

[0049] Rx is a liquid zone, in which the temperature of the coating material such as a molten resin or other such material is at or over the first form-changing temperature Ta.

[0050] Ry is a gel zone, in which the temperature of the coating material such as a molten resin or other such material is between the first form-changing temperature Ta and the second form-changing temperature Tb.

[0051] Rz is a solid zone, in which the temperature of the coating material such as a molten resin or other such material is at or below the second form-changing temperature Tb.

[0052] Referring to FIG. 7, the state of the coating material such as a molten resin or other such material in the coater head 3 is in the liquid zone Rx and in the liquid state HM-x, at or above the first form-changing temperature Ta

[0053] As to the state of the coating material such as a molten resin or other such material on the pattern surface of the intaglio roll, the coating material is in the liquid zone Rx and in the liquid state HM-x at the supply position from the coater head 3.

[0054] After that, as the temperature of the pattern surface of the intaglio roll decreases, the coating material such as a molten resin or other such material drops to or below the first form-changing temperature Ta and reaches the temperature of the gel zone Ry. In other words, the coating material is in the gel zone Ry and in the gel state HM-y.

[0055] At the transfer position, which faces the coating substrate M being transported by the high-speed coating line, the coating material such as a molten resin or other such material is also in the gel zone Ry and in the gel state HM-y.

[0056] The coating substrate M being transported by the high-speed coating line is maintained at room temperature, which is at or below the second form-changing temperature Tb.

[0057] Beyond the coating position, the coating material such as a molten resin or other such material coated to the coating substrate being transported cools down to a temperature close to that of the coating substrate M, which is at room temperature, thereby reaching the second form-changing temperature (solidification temperature), and the coating material is integrated with the coating substrate M in the solid state HM-z.

[0058] The hot melt adhesive HM-z transferred to the coating substrate will be described with reference to FIG. 8. If the coating substrate is not permeable, the hot melt adhesive is present only on one side of the coating substrate Mo (FIG. a). If the coating substrate is permeable (such as a nonwoven fabric sheet Mf), then the adhesive goes through the nonwoven fabric sheet Mf and is exposed on both sides of the nonwoven fabric sheet Mf (FIG. b).

[0059] The numerical values in the embodiment are listed below for reference. These values are not intended to limit the scope of the present invention and are only given for the purpose of showing that the invention of the present application can be implemented under these numerical values. [0060] Transport speed of coating substrate M: 50 m/minute [0061] Depth of recessed portion of intaglio roll: 0.05 to 0.5 mm [0062] Coating head temperature: 80 C. to 120 C. [0063] Temperature of intaglio roll: 50 C. to 80 C. [0064] Coating amount on coating surface: 300 g/m.sup.2 [0065] Coating temperature of coating surface: 40 C. to 60 C. [0066] Temperature of coating substrate M during transportation by coating line: room temperature [0067] Form of hot melt adhesive HM during transfer to coating substrate M: gel-state

[0068] Next, the first form-changing temperature gel point Ha and the second form-changing temperature Hb are individually set and vary depending on the properties of the coating material such as a molten resin or other such material that is being used. For the sake of reference, numerical values are given below for the hot melt adhesive used in the embodiment. [0069] First form-changing temperature Ha=80 C. to 100 C. [0070] Second form temperature change Hb=30 C. to 60 C.

INDUSTRIAL APPLICABILITY

[0071] The invention of the present application, in a system for manufacturing body fluid-absorbent products (such as sanitary napkins, disposable diapers, etc.), prevents a hot melt adhesive or the like from scattering when used to be coated on a coating material, which contributes to improve the working environment, and also contributes to develop the manufacturing industry of this type of coating device.