Hi. Does anyone have a library for the i2c expander for use with a 4x4 keypad, no information came with pcb.
I don't think so... It looks like you are too lazy to find the info 
The chip on the module is a very popular PCF8574 I2c port expander.
Google "arduino + pcf8574"will return a plenty links and info
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Do you want to interface the following (Fig-1) 4x4 Keyapd with Arduino UNO via the I2C expander?
Figure-1:
There are many on the arduino library website
You could give my library a try
There is also one for the PCF8575 for 8x8 keypads.
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That is a port expanded. There are several varieties available, 8 I/O, 16 I/O, some combinations with a D/A.
For an I2C bus expanded look at this: Multiple I2C Buses with an Arduino and TCA9548A Module