JP2011016288A - Scarf joining method of plywood - Google Patents

Abstract

PROBLEM TO BE SOLVED: To largely shorten a cycle time required for the scarf joining of plywood, and to improve productivity by employing a moisture-curable type urethane resin-based hot-melt adhesive.SOLUTION: The plywood (1) has a thickness (T) of 7.5-35 mm, a width (W) of 900-1,250 mm, and a length (L) of 1,600-5,000 mm, moisture-curable type urethane resin-based hot-melt adhesives (5) are applied on scarf slopes (3f) (3r) shaved to the scarf ratio of 1:5 to 1:10 by 100-170 g/mand cold-pressed and cured for 10-20 sec. by hydraulic cold presses (6a), (6b) at a press clamping pressure of 0.8-1.0 MPa.

Description

  The present invention relates to a method for joining scarves of plywood.

  For example, as is clear from Patent Documents 1 and 2 in the conventional method of scarf joining a plywood that is a standard flooring (about 12 mm), a thermosetting property such as a phenol resin adhesive or a melamine resin adhesive. Using a resin adhesive, it is applied to the scarf slope of the plywood and left in the heating chamber until it hardens, or is hot pressed for a certain period of time with a hot press.

JP 2002-187105 A JP 2003-94405 A

  However, the above thermosetting resin adhesive has a low viscosity and uses a large-scale hot (high frequency) press machine, but it needs to be hot-pressed for a long time until it is cured, and this is a batch process. As a result, productivity is still poor. In addition, the moisture in the adhesive during the hot pressing shifts to the surface layer and the back layer of the plywood and expands, which may cause unauthorized deformation. Become.

  The present invention aims to improve such a problem, and in order to achieve the object, in claim 1, a reactive hot melt adhesive is applied to a scarf slope of a plywood and cold-pressed by a cold press. It is characterized by.

Further, in claim 2, the plywood is made of plywood having a thickness of 7.5 to 35 mm, a width of 900 to 1250 mm and a length of 1600 to 5000 mm, and the scarf ratio is 1: 5 to 1:10. Apply 100-170 g / m ^{2 of} moisture-curing urethane resin hot melt adhesive to the slope and cool it down for 10-20 seconds with a hydraulic pressure of 0.8-1.0 MPa. It is characterized by that.

  According to the structure of Claim 1, since the scarf slopes of a plywood are cold-pressure-solidified by a cold press via a reactive hot melt (PUR) adhesive, the initial tack force is strong. By this, the press time of the post-process can be greatly shortened, and the reactive hot melt adhesive is subjected to a crosslinking reaction with moisture (humidity) in the air after solidification by cold pressure, and performs a two-stage curing action. There is an effect of obtaining excellent bonding strength.

  Also, compared to the conventional method of hot pressing a thermosetting resin adhesive with a hot press device, the plywood is not affected by moisture in the adhesive or heat at the time of pressing, so there is no risk of unauthorized deformation. Can be produced continuously and efficiently.

  In particular, if the configuration of claim 2 is adopted, the cycle time required for the scarf joint can be reduced to 2 to 4 times as much as the conventional one by setting the cycle time as 30 seconds / scarf joint. Remarkably improved.

It is a slope view which shows the structural plywood of this invention. It is explanatory drawing which shows the shaving process process of a plywood. It is explanatory drawing which shows the application | coating process of the adhesive agent with respect to a scarf slope. It is explanatory drawing which shows the pressing process of scarf slopes. It is explanatory drawing which shows from the shaving process process of a plywood to a pressing process as an automatic intermittent conveyance line.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a structural plywood (1) according to the present invention, which includes a tomato pine single plate, a larch single plate, a radiata pine (radiata pine) single piece. A softwood plywood laminated from 3 ply to 11 ply from a plate or other rotary veneer, having a width (W) of 900 mm to 1250 mm, a length (L) of 1600 mm to 5000 mm, and a thickness of 7.5 mm to 35 mm (T ).

  In the present invention, such a plywood (1) having a moisture content of 14% by weight or less, particularly preferably adjusted to 8% by weight to 14% by weight is adopted. If the moisture content exceeds 14% by weight, it is considered that the curing rate is affected. In fact, there is a risk of causing mold generation and a decrease in strength, and if it is less than 8% by weight, It absorbs moisture and tends to expand.

  And the said plywood (1) is intermittently conveyed sequentially along an automatic conveyance line, the front end part (one end part) and the rear end part (other end part) in the longitudinal direction are sawed like FIG. Each is shaved with a cutting tool (2) such as a scissors to form an upward scarf slope (3f) and a downward scarf slope (3r) having a scarf ratio of 1: 5 to 1:10. However, when the thickness (T) of the plywood (1) is 30 mm or more, the scarf ratio is set to 1: 8.

  Next, among the scarf slopes (3f) and (3r) respectively formed at the front end and the rear end of the plywood (1), the upward scarf slope (3f) on the front side in the transport direction (A) is shown in FIG. The adhesive application roll (4) is rolled along the width direction to apply the adhesive (5).

  In that case, the shaving process shown in FIG. 2 and the adhesive application process shown in FIG. 3 are described separately for convenience of explanation, but in actuality, when the plywood (1) as shown in FIG. With the cutting tool (2) and the application roll (4) attached to and integrated with the rear part of the operation, the shaving process of the upward scarf slope (3f) and the application of the adhesive immediately after that are performed in one step. The adhesive (5) is not applied to the downward scarf slope (3r) of the plywood (1).

In any case, as the adhesive (5), a reactive hot melt (PUR) adhesive, particularly a moisture-curing polyurethane resin hot melt adhesive is employed, and the coating amount is 100 g / m ^{2 to} 170 g. It is applied as / m ² .

Since such hot melt adhesives have a strong initial tack force, it is possible to shorten the pressing time (press time) in the subsequent process, and this also causes a crosslinking reaction with moisture (humidity) contained in the air even after cooling and solidification. In addition, since it is cured in two stages, there is an advantage that a high bonding strength equivalent to one type can be obtained. However, when the coating amount is larger than 170 g / m ² , the adhesive protrudes significantly during the subsequent pressing, and when the coating amount is smaller than 100 g / m ² , the upward scarf slope (3f) This is not preferable because there is a risk of occurrence of deficiency.

  Furthermore, after applying the adhesive (5) to the upward scarf slope (3f) of the plywood (1), the upward scarf slope (3f) in which the adhesive (5) is still in a molten state is shown in FIGS. Thus, it is overlapped with the downward scarf slope (3r) on the rear side of the preceding plywood (1), and 0.8 MPa to 1.0 MPa from the vertical direction by the vertical ram hydraulic cold press (6a) (6b). The adhesive (5) is cured by cold pressing for 10 to 20 seconds under a pressing pressure.

  In that case, if the pressing pressure of the cold press (6a) (6b) is higher than 1.0 MPa, the plywood (1) may be crushed, and if it is lower than 0.8 MPa, the warp is warped. In the plywood (1) in which deformation such as the above occurs, the overlapping surface (adhesion surface) does not come into close contact, so the pressure is set to 0.8 MPa to 1.0 MPa.

  Then, the adhesive (5) is a reactive hot melt (PUR) adhesive and solidifies in a short time of 10 to 20 seconds, and the scarf slopes (3f) and (3r) of the plywood (1) are bonded together. The time (cycle time) required from the shaving process of the plywood (1) shown in FIG. 5 to the bonding integration of the scarf slopes (3f) (3r) is as follows. However, at most, 30 seconds / scarf joint is sufficient, and productivity can be remarkably improved.

  Further, the reactive hot melt (PUR) adhesive does not contain water unlike the thermosetting resin adhesive used in the conventional scarf bonding method, and the plywood (1) is cooled by pressing. If pressed, it cures firmly in a short time, so no heating equipment is required and production can be carried out efficiently. Furthermore, there is no risk of causing undesired deformation such as moisture dissipation or even warping of the plywood (1), and especially the veneer used for manufacturing the plywood (1) is a softwood veneer with many missing nodes. If so, it can be markedly beneficial.

  Next, a specific example of the present invention and a comparative example which is a conventional scarf joining method will be shown.

<Example>
A structural softwood plywood having a thickness of 27 mm, a width of 910 mm, a length of 1820 mm, and a moisture content of 8 wt% was prepared by laminating and bonding 9-ply larch single veneer.

Then, such plywood is sequentially and intermittently conveyed, and while the plywood is temporarily stopped, the front end portion and the rear end portion of the plywood are each shaved with a cutting blade, and the upward scarf slope with a scarf ratio of 1: 7 A downward scarf slope and formed. In addition, immediately after the upward scarf slope of the front end portion was formed, a moisture-curable polyurethane resin hot melt (PUR) adhesive was applied to the upward scarf slope only by 130 g / m ² from above with an application roll. In that case, the temperature of the material surface was 21 ° C., and the temperature of the hot melt was 110 ° C.

  Furthermore, while such a hot melt adhesive is still in a molten state, the downward plywood downward scarf slope and the upward plywood upward scarf slope are overlapped and sandwiched by a cold press from above and below, The pressure was cold for 10 seconds (clamping time) under a pressure of 1.0 MPa.

  The cycle time required from shaving the scarf slope to the plywood to completing the press-fitting of the scarf slopes was 30 seconds / scarf joint, and the production rate could be significantly improved.

<Comparative example>
A structural softwood plywood having the same size and moisture content as in Example 1 above was prepared, and the front end portion and the rear end portion thereof were first shaved, so that an upward scarf slope and a downward scarf with a scarf ratio of 1: 7 A slope was formed.

Next, only 218 g / m ² of a thermosetting resin adhesive (mixture of melamine resin adhesive and urea resin adhesive) was applied to the upward scarf slope forming the front end of the plywood with an adhesive application roll. The material surface temperature at that time was 21 ° C.

  Furthermore, the downward scarf slope forming the rear end of the preceding plywood and the upward scarf slope of the following plywood coated with the thermosetting resin adhesive are overlapped and sandwiched from above and below by a high frequency press, Heating was performed for about 60 seconds (high-frequency oscillation time / clamping time) under a hot platen temperature of 140 ° C. and a pressing pressure of 1.1 MPa.

  The cycle time required from shaving the scarf slope to the plywood to completing the press-fitting of the scarf slopes was 90 seconds / scarf joint at the fastest. The reason why the cycle time becomes long is that a long time is required for the thermosetting resin adhesive to cure, and when the material (plywood) transport time becomes long, the cycle time is also increased. Even longer.

  In this regard, in the present invention of Example 1, the cycle time can be significantly shortened by about three times that of Comparative Example 1, and the productivity is remarkably improved.

(1) ・ Plywood (2) ・ Cutting blade (3f) ・ Upward scarf slope (3r) ・ Downward scarf slope (4) ・ Adhesive application roll (5) ・ Adhesive (6a) (6b) ・ Cold press (L ) ・ Length (T) ・ Thickness (W) ・ Width

Claims (2)

  A method for joining scarves of plywood, comprising applying a reactive hot-melt adhesive to a slope of a scarf of plywood and curing it by cold pressing. Moisture-curing plywood is made into a plywood having a thickness of 7.5 to 35 mm, a width of 900 to 1250 mm and a length of 1600 to 5000 mm, and a scarf slope having a scarf ratio of 1: 5 to 1:10. It is characterized in that a urethane resin hot melt adhesive is applied in an amount of 100 to 170 g / m ^{2 and} is cold-cured for 10 to 20 seconds under a pressing pressure of 0.8 to 1.0 MPa by a hydraulic cold press. The method for joining scarves of plywood according to claim 1.

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